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| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h4 class="title"> |
| <a name="boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics"></a><a class="link" href="detailed_semantics.html" title="Detailed Semantics">Detailed |
| Semantics</a> |
| </h4></div></div></div> |
| <p> |
| Because <code class="computeroutput"><span class="identifier">T</span></code> might be of reference |
| type, in the sequel, those entries whose semantic depends on <code class="computeroutput"><span class="identifier">T</span></code> being of reference type or not will |
| be distinguished using the following convention: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| If the entry reads: <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code><span class="emphasis"><em>(not |
| a ref)</em></span><code class="computeroutput"><span class="special">></span></code>, |
| the description corresponds only to the case where <code class="computeroutput"><span class="identifier">T</span></code> |
| is not of reference type. |
| </li> |
| <li class="listitem"> |
| If the entry reads: <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span></code>, the description corresponds |
| only to the case where <code class="computeroutput"><span class="identifier">T</span></code> |
| is of reference type. |
| </li> |
| <li class="listitem"> |
| If the entry reads: <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code>, the description is the same for |
| both cases. |
| </li> |
| </ul></div> |
| <div class="note"><table border="0" summary="Note"> |
| <tr> |
| <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../../doc/src/images/note.png"></td> |
| <th align="left">Note</th> |
| </tr> |
| <tr><td align="left" valign="top"><p> |
| The following section contains various <code class="computeroutput"><span class="identifier">assert</span><span class="special">()</span></code> which are used only to show the postconditions |
| as sample code. It is not implied that the type <code class="computeroutput"><span class="identifier">T</span></code> |
| must support each particular expression but that if the expression is |
| supported, the implied condition holds. |
| </p></td></tr> |
| </table></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <h6> |
| <a name="boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics.h0"></a> |
| <span class="phrase"><a name="boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics.optional_class_member_functions"></a></span><a class="link" href="detailed_semantics.html#boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics.optional_class_member_functions">optional |
| class member functions</a> |
| </h6> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_constructor"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">()</span> |
| <span class="keyword">noexcept</span><span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Effect:</strong></span> Default-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">uninitialized</span>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> T's default constructor <span class="underline">is not</span> called. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">def</span> <span class="special">)</span> <span class="special">;</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_constructor_none_t"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> |
| <span class="identifier">none_t</span> <span class="special">)</span> |
| <span class="keyword">noexcept</span><span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Effect:</strong></span> Constructs an <code class="computeroutput"><span class="identifier">optional</span></code> uninitialized. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">uninitialized</span>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>'s |
| default constructor <span class="underline">is not</span> called. |
| The expression <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">none</span></code> |
| denotes an instance of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">none_t</span></code> |
| that can be used as the parameter. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">none</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">n</span><span class="special">(</span><span class="identifier">none</span><span class="special">)</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">n</span> <span class="special">)</span> <span class="special">;</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_constructor_value"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> </code><span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_copy_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code> |
| is <code class="computeroutput"><span class="keyword">true</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Effect:</strong></span> Directly-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span> |
| and its value is a <span class="emphasis"><em>copy</em></span> of <code class="computeroutput"><span class="identifier">v</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> |
| <span class="special">)</span></code> throws. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> |
| <span class="special">)</span></code> is called. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only |
| be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> |
| <span class="special">);</span></code> in that case, this constructor |
| has no effect. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">optional</span><span class="special">(</span> |
| <span class="identifier">T</span><span class="special">&</span> |
| <span class="identifier">ref</span> <span class="special">)</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Effect:</strong></span> Directly-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span> |
| and its value is an instance of an internal type wrapping the reference |
| <code class="computeroutput"><span class="identifier">ref</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Throws:</strong></span> Nothing. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span> |
| <span class="identifier">T</span><span class="special">&</span> <span class="identifier">vref</span> <span class="special">=</span> <span class="identifier">v</span> <span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">vref</span><span class="special">);</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> |
| <span class="special">++</span> <span class="identifier">v</span> <span class="special">;</span> <span class="comment">// mutate referee</span> |
| <span class="identifier">assert</span> <span class="special">(*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v</span><span class="special">);</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_constructor_move_value"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> </code><span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="identifier">v</span> |
| <span class="special">)</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_move_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code> |
| is <code class="computeroutput"><span class="keyword">true</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Effect:</strong></span> Directly-Move-Constructs an |
| <code class="computeroutput"><span class="identifier">optional</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span> |
| and its value is move-constructed from <code class="computeroutput"><span class="identifier">v</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">)</span></code> |
| throws. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">)</span></code> |
| is called. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only |
| be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">);</span></code> |
| in that case, the state of <code class="computeroutput"><span class="identifier">v</span></code> |
| is determined by exception safety guarantees for <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span><span class="special">&&)</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v1</span><span class="special">,</span> <span class="identifier">v2</span><span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">v1</span><span class="special">));</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v2</span> <span class="special">)</span> <span class="special">;</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">optional</span><span class="special">(</span> |
| <span class="identifier">T</span><span class="special">&&</span> |
| <span class="identifier">ref</span> <span class="special">)</span> |
| <span class="special">=</span> <span class="keyword">delete</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> This constructor is deleted |
| </li></ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_constructor_bool_value"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> |
| <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> |
| <span class="special">::</span><span class="identifier">optional</span><span class="special">(</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> |
| <span class="identifier">T</span><span class="special">&</span> |
| <span class="identifier">v</span> <span class="special">)</span> |
| <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> |
| If condition is true, same as: |
| </li></ul></div> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span></code> |
| </p></blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> |
| <span class="special">::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> |
| otherwise, same as: |
| </li></ul></div> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> </code><span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">()</span></code> |
| </p></blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> |
| <span class="special">::</span><span class="identifier">optional</span><span class="special">()</span></code> |
| </p></blockquote></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_constructor_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> </code><span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">optional</span> |
| <span class="keyword">const</span><span class="special">&</span> |
| <span class="identifier">rhs</span> <span class="special">);</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_copy_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code> |
| is <code class="computeroutput"><span class="keyword">true</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Effect:</strong></span> Copy-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Postconditions:</strong></span> If rhs is initialized, |
| <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> |
| is initialized and its value is a <span class="emphasis"><em>copy</em></span> of the |
| value of <code class="computeroutput"><span class="identifier">rhs</span></code>; else |
| <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> |
| is uninitialized. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> |
| <span class="special">)</span></code> throws. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> If rhs is initialized, <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span></code> |
| is called. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only |
| be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> |
| <span class="special">);</span></code> in that case, this constructor |
| has no effect. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">uninit</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">uninit</span><span class="special">);</span> |
| |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">uinit2</span> <span class="special">(</span> <span class="identifier">uninit</span> <span class="special">)</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">uninit2</span> <span class="special">==</span> <span class="identifier">uninit</span> <span class="special">);</span> |
| |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">init</span><span class="special">(</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">);</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> |
| |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">init2</span> <span class="special">(</span> <span class="identifier">init</span> <span class="special">)</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">init2</span> <span class="special">==</span> <span class="identifier">init</span> <span class="special">)</span> <span class="special">;</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">optional</span><span class="special">(</span> |
| <span class="identifier">optional</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> |
| <span class="special">);</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Effect:</strong></span> Copy-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code> |
| is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> |
| is initialized and its value is another reference to the same object |
| referenced by <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>; |
| else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> |
| is uninitialized. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Throws:</strong></span> Nothing. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code> |
| is initialized, both <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> will refer to the same object |
| (they alias). |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">uninit</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">uninit</span><span class="special">);</span> |
| |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">uinit2</span> <span class="special">(</span> <span class="identifier">uninit</span> <span class="special">)</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">uninit2</span> <span class="special">==</span> <span class="identifier">uninit</span> <span class="special">);</span> |
| |
| <span class="identifier">T</span> <span class="identifier">v</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">ref</span> <span class="special">=</span> <span class="identifier">v</span> <span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">init</span><span class="special">(</span><span class="identifier">ref</span><span class="special">);</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> |
| |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">init2</span> <span class="special">(</span> <span class="identifier">init</span> <span class="special">)</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init2</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> |
| |
| <span class="identifier">v</span> <span class="special">=</span> <span class="number">3</span> <span class="special">;</span> |
| |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="number">3</span> <span class="special">)</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init2</span> <span class="special">==</span> <span class="number">3</span> <span class="special">)</span> <span class="special">;</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_move_constructor_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> </code><span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">optional</span><span class="special">&&</span> <span class="identifier">rhs</span> |
| <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">(</span></code><span class="emphasis"><em>see below</em></span><code class="computeroutput"><span class="special">);</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_move_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code> |
| is <code class="computeroutput"><span class="keyword">true</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Effect:</strong></span> Move-constructs an <code class="computeroutput"><span class="identifier">optional</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code> |
| is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> |
| is initialized and its value is move constructed from <code class="computeroutput"><span class="identifier">rhs</span></code>; else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is uninitialized. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">)</span></code> |
| throws. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Remarks:</strong></span> The expression inside <code class="computeroutput"><span class="keyword">noexcept</span></code> is equivalent to <code class="computeroutput"><span class="identifier">is_nothrow_move_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code> |
| is initialized, <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="special">&&</span> |
| <span class="special">)</span></code> is called. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only |
| be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">);</span></code> |
| in that case, <code class="computeroutput"><span class="identifier">rhs</span></code> remains |
| initialized and the value of <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> is determined by exception safety |
| of <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span><span class="special">&&)</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span> <span class="identifier">uninit</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">uninit</span><span class="special">);</span> |
| |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span> <span class="identifier">uinit2</span> <span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">uninit</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">uninit2</span> <span class="special">==</span> <span class="identifier">uninit</span> <span class="special">);</span> |
| |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span> <span class="identifier">init</span><span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">uniqye_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="keyword">new</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">))</span> <span class="special">);</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">**</span><span class="identifier">init</span> <span class="special">==</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> |
| |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span> <span class="identifier">init2</span> <span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">init</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">init</span> <span class="special">);</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="keyword">nullptr</span> <span class="special">);</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">init2</span> <span class="special">);</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">**</span><span class="identifier">init2</span> <span class="special">==</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">optional</span><span class="special">(</span> |
| <span class="identifier">optional</span> <span class="special">&&</span> |
| <span class="identifier">rhs</span> <span class="special">);</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Effect:</strong></span> Move-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code> |
| is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> |
| is initialized and its value is another reference to the same object |
| referenced by <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>; |
| else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> |
| is uninitialized. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Throws:</strong></span> Nothing. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code> |
| is initialized, both <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> will refer to the same object |
| (they alias). |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&></span> <span class="identifier">uninit</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">uninit</span><span class="special">);</span> |
| |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&></span> <span class="identifier">uinit2</span> <span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">uninit</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">uninit2</span> <span class="special">==</span> <span class="identifier">uninit</span> <span class="special">);</span> |
| |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">v</span><span class="special">(</span><span class="keyword">new</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">))</span> <span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&></span> <span class="identifier">init</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> |
| |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&></span> <span class="identifier">init2</span> <span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">init</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init2</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> |
| |
| <span class="special">*</span><span class="identifier">v</span> <span class="special">=</span> <span class="number">3</span> <span class="special">;</span> |
| |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">**</span><span class="identifier">init</span> <span class="special">==</span> <span class="number">3</span> <span class="special">)</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">**</span><span class="identifier">init2</span> <span class="special">==</span> <span class="number">3</span> <span class="special">)</span> <span class="special">;</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_constructor_other_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> |
| <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> <span class="special">);</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Effect:</strong></span> Copy-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code> |
| is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> |
| is initialized and its value is a <span class="emphasis"><em>copy</em></span> of the |
| value of rhs converted to type <code class="computeroutput"><span class="identifier">T</span></code>; |
| else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> |
| is uninitialized. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span> <span class="keyword">const</span><span class="special">&</span> |
| <span class="special">)</span></code> throws. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span> <span class="keyword">const</span><span class="special">&</span> |
| <span class="special">)</span></code> is called if <code class="computeroutput"><span class="identifier">rhs</span></code> is initialized, which requires |
| a valid conversion from <code class="computeroutput"><span class="identifier">U</span></code> |
| to <code class="computeroutput"><span class="identifier">T</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only |
| be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span> <span class="keyword">const</span><span class="special">&</span> |
| <span class="special">);</span></code> in that case, this constructor |
| has no effect. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">x</span><span class="special">(</span><span class="number">123.4</span><span class="special">);</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">x</span> <span class="special">==</span> <span class="number">123.4</span> <span class="special">)</span> <span class="special">;</span> |
| |
| <span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">y</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span> <span class="special">;</span> |
| <span class="identifier">assert</span><span class="special">(</span> <span class="special">*</span><span class="identifier">y</span> <span class="special">==</span> <span class="number">123</span> <span class="special">)</span> <span class="special">;</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_move_constructor_other_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> |
| <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">>&&</span> |
| <span class="identifier">rhs</span> <span class="special">);</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Effect:</strong></span> Move-constructs an <code class="computeroutput"><span class="identifier">optional</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code> |
| is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> |
| is initialized and its value is move-constructed from <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>; |
| else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> |
| is uninitialized. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span><span class="special">&&</span> <span class="special">)</span></code> |
| throws. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span><span class="special">&&</span> <span class="special">)</span></code> |
| is called if <code class="computeroutput"><span class="identifier">rhs</span></code> is |
| initialized, which requires a valid conversion from <code class="computeroutput"><span class="identifier">U</span></code> |
| to <code class="computeroutput"><span class="identifier">T</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only |
| be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span><span class="special">&&</span> <span class="special">);</span></code> |
| in that case, <code class="computeroutput"><span class="identifier">rhs</span></code> remains |
| initialized and the value of <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> is determined by exception safety |
| guarantee of <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span><span class="special">&&</span> |
| <span class="special">)</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">x</span><span class="special">(</span><span class="number">123.4</span><span class="special">);</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">x</span> <span class="special">==</span> <span class="number">123.4</span> <span class="special">)</span> <span class="special">;</span> |
| |
| <span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">y</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">x</span><span class="special">))</span> <span class="special">;</span> |
| <span class="identifier">assert</span><span class="special">(</span> <span class="special">*</span><span class="identifier">y</span> <span class="special">==</span> <span class="number">123</span> <span class="special">)</span> <span class="special">;</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_constructor_factory"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">InPlaceFactory</span><span class="special">></span> |
| <span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> |
| <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> |
| <span class="identifier">InPlaceFactory</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">f</span> <span class="special">);</span></code> |
| </p></blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">TypedInPlaceFactory</span><span class="special">></span> |
| <span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> |
| <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> |
| <span class="identifier">TypedInPlaceFactory</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">f</span> <span class="special">);</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Effect:</strong></span> Constructs an <code class="computeroutput"><span class="identifier">optional</span></code> with a value of <code class="computeroutput"><span class="identifier">T</span></code> obtained from the factory. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span> |
| and its value is <span class="emphasis"><em>directly given</em></span> from the factory |
| <code class="computeroutput"><span class="identifier">f</span></code> (i.e., the value |
| <span class="underline">is not copied</span>). |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Throws:</strong></span> Whatever the <code class="computeroutput"><span class="identifier">T</span></code> constructor called by the factory |
| throws. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> See <a class="link" href="../../tutorial/in_place_factories.html" title="In-Place Factories">In-Place |
| Factories</a> |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only |
| be thrown during the call to the <code class="computeroutput"><span class="identifier">T</span></code> |
| constructor used by the factory; in that case, this constructor has |
| no effect. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="keyword">class</span> <span class="identifier">C</span> <span class="special">{</span> <span class="identifier">C</span> <span class="special">(</span> <span class="keyword">char</span><span class="special">,</span> <span class="keyword">double</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="special">)</span> <span class="special">;</span> <span class="special">}</span> <span class="special">;</span> |
| |
| <span class="identifier">C</span> <span class="identifier">v</span><span class="special">(</span><span class="char">'A'</span><span class="special">,</span><span class="number">123.4</span><span class="special">,</span><span class="string">"hello"</span><span class="special">);</span> |
| |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">C</span><span class="special">></span> <span class="identifier">x</span><span class="special">(</span> <span class="identifier">in_place</span> <span class="special">(</span><span class="char">'A'</span><span class="special">,</span> <span class="number">123.4</span><span class="special">,</span> <span class="string">"hello"</span><span class="special">)</span> <span class="special">);</span> <span class="comment">// InPlaceFactory used</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">C</span><span class="special">></span> <span class="identifier">y</span><span class="special">(</span> <span class="identifier">in_place</span><span class="special"><</span><span class="identifier">C</span><span class="special">>(</span><span class="char">'A'</span><span class="special">,</span> <span class="number">123.4</span><span class="special">,</span> <span class="string">"hello"</span><span class="special">)</span> <span class="special">);</span> <span class="comment">// TypedInPlaceFactory used</span> |
| |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">x</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">y</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_operator_equal_none_t"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">none_t</span> |
| <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Effect:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized destroys its contained |
| value. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is uninitialized. |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_operator_equal_value"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span> |
| <span class="keyword">const</span><span class="special">&</span> |
| <span class="identifier">rhs</span> <span class="special">)</span> |
| <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Effect:</strong></span> Assigns the value <code class="computeroutput"><span class="identifier">rhs</span></code> to an <code class="computeroutput"><span class="identifier">optional</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized and its value is |
| a <span class="emphasis"><em>copy</em></span> of <code class="computeroutput"><span class="identifier">rhs</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> |
| <span class="special">)</span></code> or <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&)</span></code> |
| throws. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> was initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s assignment operator is used, |
| otherwise, its copy-constructor is used. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Exception Safety:</strong></span> In the event of |
| an exception, the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is unchanged and its value unspecified |
| as far as <code class="computeroutput"><span class="identifier">optional</span></code> |
| is concerned (it is up to <code class="computeroutput"><span class="identifier">T</span></code>'s |
| <code class="computeroutput"><span class="keyword">operator</span><span class="special">=()</span></code>). |
| If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> |
| is initially uninitialized and <code class="computeroutput"><span class="identifier">T</span></code>'s |
| <span class="emphasis"><em>copy constructor</em></span> fails, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is left properly uninitialized. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span> <span class="special">;</span> |
| |
| <span class="identifier">T</span> <span class="identifier">y</span><span class="special">;</span> |
| <span class="identifier">def</span> <span class="special">=</span> <span class="identifier">y</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def</span> <span class="special">==</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span> |
| <span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">y</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>&</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">rhs</span> |
| <span class="special">)</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Effect:</strong></span> (Re)binds the wrapped reference. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized and it references |
| the same object referenced by <code class="computeroutput"><span class="identifier">rhs</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> was initialized, it is <span class="emphasis"><em>rebound</em></span> |
| to the new object. See <a class="link" href="../../tutorial/rebinding_semantics_for_assignment_of_optional_references.html" title="Rebinding semantics for assignment of optional references">here</a> |
| for details on this behavior. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="keyword">int</span> <span class="identifier">a</span> <span class="special">=</span> <span class="number">1</span> <span class="special">;</span> |
| <span class="keyword">int</span> <span class="identifier">b</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span> |
| <span class="identifier">T</span><span class="special">&</span> <span class="identifier">ra</span> <span class="special">=</span> <span class="identifier">a</span> <span class="special">;</span> |
| <span class="identifier">T</span><span class="special">&</span> <span class="identifier">rb</span> <span class="special">=</span> <span class="identifier">b</span> <span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">def</span> <span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">ra</span><span class="special">)</span> <span class="special">;</span> |
| |
| <span class="identifier">def</span> <span class="special">=</span> <span class="identifier">rb</span> <span class="special">;</span> <span class="comment">// binds 'def' to 'b' through 'rb'</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def</span> <span class="special">==</span> <span class="identifier">b</span> <span class="special">)</span> <span class="special">;</span> |
| <span class="special">*</span><span class="identifier">def</span> <span class="special">=</span> <span class="identifier">a</span> <span class="special">;</span> <span class="comment">// changes the value of 'b' to a copy of the value of 'a'</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">b</span> <span class="special">==</span> <span class="identifier">a</span> <span class="special">)</span> <span class="special">;</span> |
| <span class="keyword">int</span> <span class="identifier">c</span> <span class="special">=</span> <span class="number">3</span><span class="special">;</span> |
| <span class="keyword">int</span><span class="special">&</span> <span class="identifier">rc</span> <span class="special">=</span> <span class="identifier">c</span> <span class="special">;</span> |
| <span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">rc</span> <span class="special">;</span> <span class="comment">// REBINDS to 'c' through 'rc'</span> |
| <span class="identifier">c</span> <span class="special">=</span> <span class="number">4</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="number">4</span> <span class="special">)</span> <span class="special">;</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_operator_move_equal_value"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="identifier">rhs</span> |
| <span class="special">)</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Effect:</strong></span> Moves the value <code class="computeroutput"><span class="identifier">rhs</span></code> to an <code class="computeroutput"><span class="identifier">optional</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized and its value is |
| moved from <code class="computeroutput"><span class="identifier">rhs</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">)</span></code> |
| or <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span> <span class="special">&&)</span></code> |
| throws. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> was initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s move-assignment operator is used, |
| otherwise, its move-constructor is used. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Exception Safety:</strong></span> In the event of |
| an exception, the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is unchanged and its value unspecified |
| as far as <code class="computeroutput"><span class="identifier">optional</span></code> |
| is concerned (it is up to <code class="computeroutput"><span class="identifier">T</span></code>'s |
| <code class="computeroutput"><span class="keyword">operator</span><span class="special">=()</span></code>). |
| If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> |
| is initially uninitialized and <code class="computeroutput"><span class="identifier">T</span></code>'s |
| <span class="emphasis"><em>move constructor</em></span> fails, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is left properly uninitialized. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span> <span class="special">;</span> |
| |
| <span class="identifier">T</span> <span class="identifier">y1</span><span class="special">,</span> <span class="identifier">y2</span><span class="special">,</span> <span class="identifier">yR</span><span class="special">;</span> |
| <span class="identifier">def</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">y1</span><span class="special">)</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def</span> <span class="special">==</span> <span class="identifier">yR</span> <span class="special">)</span> <span class="special">;</span> |
| <span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">y2</span><span class="special">)</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">yR</span> <span class="special">)</span> <span class="special">;</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>&</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="identifier">rhs</span> |
| <span class="special">)</span> <span class="special">=</span> |
| <span class="keyword">delete</span><span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> This assignment operator is |
| deleted. |
| </li></ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_operator_equal_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span> |
| <span class="keyword">const</span><span class="special">&</span> |
| <span class="identifier">rhs</span> <span class="special">)</span> |
| <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code> |
| is <a href="../../../../../../utility/CopyConstructible.html" target="_top"><code class="computeroutput"><span class="identifier">CopyConstructible</span></code></a> and <code class="computeroutput"><span class="identifier">CopyAssignable</span></code>. |
| </li> |
| <li class="listitem"> |
| <p class="simpara"> |
| <span class="bold"><strong>Effects:</strong></span> |
| </p> |
| <div class="informaltable"><table class="table"> |
| <colgroup> |
| <col> |
| <col> |
| <col> |
| </colgroup> |
| <thead><tr> |
| <th> |
| </th> |
| <th> |
| <p> |
| <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> |
| contains a value |
| </p> |
| </th> |
| <th> |
| <p> |
| <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> |
| does not contain a value |
| </p> |
| </th> |
| </tr></thead> |
| <tbody> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="identifier">rhs</span></code> contains |
| a value |
| </p> |
| </td> |
| <td> |
| <p> |
| assigns <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> |
| to the contained value |
| </p> |
| </td> |
| <td> |
| <p> |
| initializes the contained value as if direct-initializing |
| an object of type <code class="computeroutput"><span class="identifier">T</span></code> |
| with <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="identifier">rhs</span></code> does |
| not contain a value |
| </p> |
| </td> |
| <td> |
| <p> |
| destroys the contained value by calling <code class="computeroutput"><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| no effect |
| </p> |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>; |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Exception Safety:</strong></span> If any exception |
| is thrown, the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="identifier">rhs</span></code> |
| remains unchanged. If an exception is thrown during the call to <code class="computeroutput"><span class="identifier">T</span></code>'s copy constructor, no effect. |
| If an exception is thrown during the call to <code class="computeroutput"><span class="identifier">T</span></code>'s |
| copy assignment, the state of its contained value is as defined by |
| the exception safety guarantee of <code class="computeroutput"><span class="identifier">T</span></code>'s |
| copy assignment. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span> |
| |
| <span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">def</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">def</span> <span class="special">)</span> <span class="special">;</span> |
| <span class="comment">// previous value (copy of 'v') destroyed from within 'opt'.</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> |
| <span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> |
| <span class="special">)</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Effect:</strong></span> (Re)binds thee wrapped reference. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> |
| is initialized and it references the same object referenced by <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>; |
| otherwise, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> |
| is uninitialized (and references no object). |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> was initialized and so is <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>, |
| <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> |
| is <span class="emphasis"><em>rebound</em></span> to the new object. See <a class="link" href="../../tutorial/rebinding_semantics_for_assignment_of_optional_references.html" title="Rebinding semantics for assignment of optional references">here</a> |
| for details on this behavior. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="keyword">int</span> <span class="identifier">a</span> <span class="special">=</span> <span class="number">1</span> <span class="special">;</span> |
| <span class="keyword">int</span> <span class="identifier">b</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span> |
| <span class="identifier">T</span><span class="special">&</span> <span class="identifier">ra</span> <span class="special">=</span> <span class="identifier">a</span> <span class="special">;</span> |
| <span class="identifier">T</span><span class="special">&</span> <span class="identifier">rb</span> <span class="special">=</span> <span class="identifier">b</span> <span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">def</span> <span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">ora</span><span class="special">(</span><span class="identifier">ra</span><span class="special">)</span> <span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">orb</span><span class="special">(</span><span class="identifier">rb</span><span class="special">)</span> <span class="special">;</span> |
| |
| <span class="identifier">def</span> <span class="special">=</span> <span class="identifier">orb</span> <span class="special">;</span> <span class="comment">// binds 'def' to 'b' through 'rb' wrapped within 'orb'</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def</span> <span class="special">==</span> <span class="identifier">b</span> <span class="special">)</span> <span class="special">;</span> |
| <span class="special">*</span><span class="identifier">def</span> <span class="special">=</span> <span class="identifier">ora</span> <span class="special">;</span> <span class="comment">// changes the value of 'b' to a copy of the value of 'a'</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">b</span> <span class="special">==</span> <span class="identifier">a</span> <span class="special">)</span> <span class="special">;</span> |
| <span class="keyword">int</span> <span class="identifier">c</span> <span class="special">=</span> <span class="number">3</span><span class="special">;</span> |
| <span class="keyword">int</span><span class="special">&</span> <span class="identifier">rc</span> <span class="special">=</span> <span class="identifier">c</span> <span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">orc</span><span class="special">(</span><span class="identifier">rc</span><span class="special">)</span> <span class="special">;</span> |
| <span class="identifier">ora</span> <span class="special">=</span> <span class="identifier">orc</span> <span class="special">;</span> <span class="comment">// REBINDS ora to 'c' through 'rc'</span> |
| <span class="identifier">c</span> <span class="special">=</span> <span class="number">4</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">ora</span> <span class="special">==</span> <span class="number">4</span> <span class="special">)</span> <span class="special">;</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_operator_move_equal_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&&</span> <span class="identifier">rhs</span> |
| <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">(</span></code><span class="emphasis"><em>see below</em></span><code class="computeroutput"><span class="special">);</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code> |
| is <code class="computeroutput"><span class="identifier">MoveConstructible</span></code> |
| and <code class="computeroutput"><span class="identifier">MoveAssignable</span></code>. |
| </li> |
| <li class="listitem"> |
| <p class="simpara"> |
| <span class="bold"><strong>Effects:</strong></span> |
| </p> |
| <div class="informaltable"><table class="table"> |
| <colgroup> |
| <col> |
| <col> |
| <col> |
| </colgroup> |
| <thead><tr> |
| <th> |
| </th> |
| <th> |
| <p> |
| <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> |
| contains a value |
| </p> |
| </th> |
| <th> |
| <p> |
| <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> |
| does not contain a value |
| </p> |
| </th> |
| </tr></thead> |
| <tbody> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="identifier">rhs</span></code> contains |
| a value |
| </p> |
| </td> |
| <td> |
| <p> |
| assigns <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code> to the contained value |
| </p> |
| </td> |
| <td> |
| <p> |
| initializes the contained value as if direct-initializing |
| an object of type <code class="computeroutput"><span class="identifier">T</span></code> |
| with <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code> |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="identifier">rhs</span></code> does |
| not contain a value |
| </p> |
| </td> |
| <td> |
| <p> |
| destroys the contained value by calling <code class="computeroutput"><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| no effect |
| </p> |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>; |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Remarks:</strong></span> The expression inside <code class="computeroutput"><span class="keyword">noexcept</span></code> is equivalent to <code class="computeroutput"><span class="identifier">is_nothrow_move_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span> <span class="special">&&</span> |
| <span class="identifier">is_nothrow_move_assignable</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Exception Safety:</strong></span> If any exception |
| is thrown, the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="identifier">rhs</span></code> |
| remains unchanged. If an exception is thrown during the call to <code class="computeroutput"><span class="identifier">T</span></code>'s move constructor, the state of |
| <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> |
| is determined by the exception safety guarantee of <code class="computeroutput"><span class="identifier">T</span></code>'s |
| move constructor. If an exception is thrown during the call to T's |
| move-assignment, the state of <code class="computeroutput"><span class="special">**</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> is determined by the exception |
| safety guarantee of T's move assignment. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">))</span> <span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span> |
| |
| <span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">def</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">def</span> <span class="special">)</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> |
| <span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>&&</span> <span class="identifier">rhs</span> |
| <span class="special">)</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> |
| <span class="bold"><strong>Effect:</strong></span> Same as <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> |
| <span class="keyword">const</span><span class="special">&</span> |
| <span class="identifier">rhs</span> <span class="special">)</span></code>. |
| </li></ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_operator_equal_other_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="identifier">optional</span><span class="special">&</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> |
| <span class="special">)</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <p class="simpara"> |
| <span class="bold"><strong>Effect:</strong></span> |
| </p> |
| <div class="informaltable"><table class="table"> |
| <colgroup> |
| <col> |
| <col> |
| <col> |
| </colgroup> |
| <thead><tr> |
| <th> |
| </th> |
| <th> |
| <p> |
| <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> |
| contains a value |
| </p> |
| </th> |
| <th> |
| <p> |
| <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> |
| does not contain a value |
| </p> |
| </th> |
| </tr></thead> |
| <tbody> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="identifier">rhs</span></code> contains |
| a value |
| </p> |
| </td> |
| <td> |
| <p> |
| assigns <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> |
| to the contained value |
| </p> |
| </td> |
| <td> |
| <p> |
| initializes the contained value as if direct-initializing |
| an object of type <code class="computeroutput"><span class="identifier">T</span></code> |
| with <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="identifier">rhs</span></code> does |
| not contain a value |
| </p> |
| </td> |
| <td> |
| <p> |
| destroys the contained value by calling <code class="computeroutput"><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| no effect |
| </p> |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Exception Safety:</strong></span> If any exception |
| is thrown, the result of the expression <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code> remains unchanged. If an exception |
| is thrown during the call to <code class="computeroutput"><span class="identifier">T</span></code>'s |
| constructor, no effect. If an exception is thrown during the call to |
| <code class="computeroutput"><span class="identifier">T</span></code>'s assignment, the |
| state of its contained value is as defined by the exception safety |
| guarantee of <code class="computeroutput"><span class="identifier">T</span></code>'s copy |
| assignment. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt0</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="identifier">opt1</span><span class="special">;</span> |
| |
| <span class="identifier">opt1</span> <span class="special">=</span> <span class="identifier">opt0</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt1</span> <span class="special">==</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="identifier">U</span><span class="special">>(</span><span class="identifier">v</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_operator_move_equal_other_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="identifier">optional</span><span class="special">&</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">>&&</span> <span class="identifier">rhs</span> |
| <span class="special">)</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <p class="simpara"> |
| <span class="bold"><strong>Effect:</strong></span> |
| </p> |
| <div class="informaltable"><table class="table"> |
| <colgroup> |
| <col> |
| <col> |
| <col> |
| </colgroup> |
| <thead><tr> |
| <th> |
| </th> |
| <th> |
| <p> |
| <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> |
| contains a value |
| </p> |
| </th> |
| <th> |
| <p> |
| <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> |
| does not contain a value |
| </p> |
| </th> |
| </tr></thead> |
| <tbody> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="identifier">rhs</span></code> contains |
| a value |
| </p> |
| </td> |
| <td> |
| <p> |
| assigns <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code> to the contained value |
| </p> |
| </td> |
| <td> |
| <p> |
| initializes the contained value as if direct-initializing |
| an object of type <code class="computeroutput"><span class="identifier">T</span></code> |
| with <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code> |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="identifier">rhs</span></code> does |
| not contain a value |
| </p> |
| </td> |
| <td> |
| <p> |
| destroys the contained value by calling <code class="computeroutput"><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| no effect |
| </p> |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Exception Safety:</strong></span> If any exception |
| is thrown, the result of the expression <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code> remains unchanged. If an exception |
| is thrown during the call to <code class="computeroutput"><span class="identifier">T</span></code>'s |
| constructor, no effect. If an exception is thrown during the call to |
| <code class="computeroutput"><span class="identifier">T</span></code>'s assignment, the |
| state of its contained value is as defined by the exception safety |
| guarantee of <code class="computeroutput"><span class="identifier">T</span></code>'s copy |
| assignment. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt0</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="identifier">opt1</span><span class="special">;</span> |
| |
| <span class="identifier">opt1</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">opt0</span><span class="special">)</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt0</span> <span class="special">);</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt1</span> <span class="special">)</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt1</span> <span class="special">==</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="identifier">U</span><span class="special">>(</span><span class="identifier">v</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_emplace"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span><span class="special">...</span> <span class="identifier">Args</span><span class="special">></span> |
| <span class="keyword">void</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> |
| <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">emplace</span><span class="special">(</span> |
| <span class="identifier">Args</span><span class="special">...&&</span> |
| <span class="identifier">args</span> <span class="special">);</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Requires:</strong></span> The compiler supports rvalue |
| references and variadic templates. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Effect:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized calls <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span> <span class="special">=</span> <span class="identifier">none</span></code>. |
| Then initializes in-place the contained value as if direct-initializing |
| an object of type <code class="computeroutput"><span class="identifier">T</span></code> |
| with <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special"><</span><span class="identifier">Args</span><span class="special">>(</span><span class="identifier">args</span><span class="special">)...</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Throws:</strong></span> Whatever the selected <code class="computeroutput"><span class="identifier">T</span></code>'s constructor throws. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code> |
| need not be <code class="computeroutput"><span class="identifier">MoveConstructible</span></code> |
| or <code class="computeroutput"><span class="identifier">MoveAssignable</span></code>. |
| On compilers that do not support variadic templates, the signature |
| falls back to single-argument: <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> |
| <span class="identifier">Arg</span><span class="special">></span> |
| <span class="keyword">void</span> <span class="identifier">emplace</span><span class="special">(</span><span class="identifier">Arg</span><span class="special">&&</span> <span class="identifier">arg</span><span class="special">)</span></code>. On compilers that do not support |
| rvalue references, the signature falls back to two overloads: taking |
| <code class="computeroutput"><span class="keyword">const</span></code> and non-<code class="computeroutput"><span class="keyword">const</span></code> lvalue reference. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Exception Safety:</strong></span> If an exception |
| is thrown during the initialization of <code class="computeroutput"><span class="identifier">T</span></code>, |
| <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> |
| is <span class="emphasis"><em>uninitialized</em></span>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="keyword">const</span> <span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">;</span> |
| <span class="identifier">opt</span><span class="special">.</span><span class="identifier">emplace</span><span class="special">(</span><span class="number">0</span><span class="special">);</span> <span class="comment">// create in-place using ctor T(int)</span> |
| <span class="identifier">opt</span><span class="special">.</span><span class="identifier">emplace</span><span class="special">();</span> <span class="comment">// destroy previous and default-construct another T</span> |
| <span class="identifier">opt</span><span class="special">.</span><span class="identifier">emplace</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span> <span class="comment">// destroy and copy-construct in-place (no assignment called)</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_operator_equal_factory"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">InPlaceFactory</span><span class="special">></span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">InPlaceFactory</span> |
| <span class="keyword">const</span><span class="special">&</span> |
| <span class="identifier">f</span> <span class="special">);</span></code> |
| </p></blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">TypedInPlaceFactory</span><span class="special">></span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">TypedInPlaceFactory</span> |
| <span class="keyword">const</span><span class="special">&</span> |
| <span class="identifier">f</span> <span class="special">);</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Effect:</strong></span> Assigns an <code class="computeroutput"><span class="identifier">optional</span></code> |
| with a value of <code class="computeroutput"><span class="identifier">T</span></code> obtained |
| from the factory. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span> |
| and its value is <span class="emphasis"><em>directly given</em></span> from the factory |
| <code class="computeroutput"><span class="identifier">f</span></code> (i.e., the value |
| <span class="underline">is not copied</span>). |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Throws:</strong></span> Whatever the <code class="computeroutput"><span class="identifier">T</span></code> constructor called by the factory |
| throws. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> See <a class="link" href="../../tutorial/in_place_factories.html" title="In-Place Factories">In-Place |
| Factories</a> |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only |
| be thrown during the call to the <code class="computeroutput"><span class="identifier">T</span></code> |
| constructor used by the factory; in that case, the <code class="computeroutput"><span class="identifier">optional</span></code> |
| object will be reset to be <span class="emphasis"><em>uninitialized</em></span>. |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_reset_value"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">void</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> |
| <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">reset</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> |
| <span class="bold"><strong>Deprecated:</strong></span> same as <code class="computeroutput"><span class="keyword">operator</span><span class="special">=</span> |
| <span class="special">(</span> <span class="identifier">T</span> |
| <span class="keyword">const</span><span class="special">&</span> |
| <span class="identifier">v</span><span class="special">)</span> |
| <span class="special">;</span></code> |
| </li></ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_reset"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">void</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">reset</span><span class="special">()</span> <span class="keyword">noexcept</span> |
| <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> |
| <span class="bold"><strong>Deprecated:</strong></span> Same as <code class="computeroutput"><span class="keyword">operator</span><span class="special">=(</span> |
| <span class="identifier">none_t</span> <span class="special">);</span></code> |
| </li></ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_get"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> |
| <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get</span><span class="special">()</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span> |
| <span class="keyword">const</span><span class="special">&</span> |
| <span class="identifier">get</span> <span class="special">(</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">get</span> |
| <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> |
| <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span> |
| <span class="special">&)</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Returns:</strong></span> A reference to the contained |
| value |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Throws:</strong></span> Nothing. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> The requirement is asserted |
| via <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>. |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">get</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">get</span><span class="special">()</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span> |
| <span class="keyword">const</span><span class="special">&</span> |
| <span class="identifier">get</span> <span class="special">(</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> |
| <span class="keyword">const</span><span class="special">&</span> |
| <span class="special">)</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">get</span> |
| <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="special">&)</span> |
| <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Requires: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Returns:</strong></span> <span class="underline">The</span> |
| reference contained. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Throws:</strong></span> Nothing. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> The requirement is asserted |
| via <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>. |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_operator_asterisk"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> |
| <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">*()</span> |
| <span class="keyword">const</span><span class="special">&</span> |
| <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">*()</span> <span class="special">&;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Returns:</strong></span> A reference to the contained |
| value |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Throws:</strong></span> Nothing. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> The requirement is asserted |
| via <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>. |
| On compilers that do not support ref-qualifiers on member functions |
| these two overloads are replaced with the classical two: a <code class="computeroutput"><span class="keyword">const</span></code> and non-<code class="computeroutput"><span class="keyword">const</span></code> |
| member functions. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span> <span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">(</span> <span class="identifier">v</span> <span class="special">);</span> |
| <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">u</span> <span class="special">=</span> <span class="special">*</span><span class="identifier">opt</span><span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">u</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> |
| <span class="identifier">T</span> <span class="identifier">w</span> <span class="special">;</span> |
| <span class="special">*</span><span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">w</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">w</span> <span class="special">)</span> <span class="special">;</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_operator_asterisk_move"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">T</span><span class="special">&&</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">*()</span> <span class="special">&&;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> contains a value. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">return</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">val</span><span class="special">);</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> The requirement is asserted |
| via <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>. |
| On compilers that do not support ref-qualifiers on member functions |
| this overload is not present. |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">T</span> <span class="special">&</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">*()</span> |
| <span class="keyword">const</span><span class="special">&</span> |
| <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">T</span> <span class="special">&</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">*()</span> |
| <span class="special">&</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">T</span> <span class="special">&</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">*()</span> |
| <span class="special">&&</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Requires: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Returns:</strong></span> <span class="underline">The</span> |
| reference contained. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Throws:</strong></span> Nothing. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> The requirement is asserted |
| via <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>. |
| On compilers that do not support ref-qualifiers on member functions |
| these three overloads are replaced with the classical two: a <code class="computeroutput"><span class="keyword">const</span></code> and non-<code class="computeroutput"><span class="keyword">const</span></code> |
| member functions. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span> <span class="special">;</span> |
| <span class="identifier">T</span><span class="special">&</span> <span class="identifier">vref</span> <span class="special">=</span> <span class="identifier">v</span> <span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">opt</span> <span class="special">(</span> <span class="identifier">vref</span> <span class="special">);</span> |
| <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">vref2</span> <span class="special">=</span> <span class="special">*</span><span class="identifier">opt</span><span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">vref2</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> |
| <span class="special">++</span> <span class="identifier">v</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_value"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span><span class="special">()</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span><span class="special">()</span> <span class="special">&</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">return</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">?</span> <span class="special">*</span><span class="identifier">val</span> <span class="special">:</span> <span class="keyword">throw</span> <span class="identifier">bad_optional_access</span><span class="special">();</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> On compilers that do not support |
| ref-qualifiers on member functions these two overloads are replaced |
| with the classical two: a <code class="computeroutput"><span class="keyword">const</span></code> |
| and non-<code class="computeroutput"><span class="keyword">const</span></code> member functions. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span> <span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">o0</span><span class="special">,</span> <span class="identifier">o1</span> <span class="special">(</span> <span class="identifier">v</span> <span class="special">);</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span><span class="special">.</span><span class="identifier">value</span><span class="special">()</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">);</span> |
| |
| <span class="keyword">try</span> <span class="special">{</span> |
| <span class="identifier">o0</span><span class="special">.</span><span class="identifier">value</span><span class="special">();</span> <span class="comment">// throws</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="keyword">false</span> <span class="special">);</span> |
| <span class="special">}</span> |
| <span class="keyword">catch</span><span class="special">(</span><span class="identifier">bad_optional_access</span><span class="special">&)</span> <span class="special">{</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="keyword">true</span> <span class="special">);</span> |
| <span class="special">}</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_value_move"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">T</span><span class="special">&&</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span><span class="special">()</span> <span class="special">&&</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">return</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">?</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">val</span><span class="special">)</span> <span class="special">:</span> <span class="keyword">throw</span> <span class="identifier">bad_optional_access</span><span class="special">();</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> On compilers that do not support |
| ref-qualifiers on member functions this overload is not present. |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_value_or"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="identifier">T</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value_or</span><span class="special">(</span><span class="identifier">U</span> <span class="special">&&</span> |
| <span class="identifier">v</span><span class="special">)</span> |
| <span class="keyword">const</span><span class="special">&</span> |
| <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">if</span> <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="special">**</span><span class="keyword">this</span><span class="special">;</span> <span class="keyword">else</span> <span class="keyword">return</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special"><</span><span class="identifier">U</span><span class="special">>(</span><span class="identifier">v</span><span class="special">);</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Remarks:</strong></span> If <code class="computeroutput"><span class="identifier">T</span></code> |
| is not <a href="../../../../../../utility/CopyConstructible.html" target="_top"><code class="computeroutput"><span class="identifier">CopyConstructible</span></code></a> or <code class="computeroutput"><span class="identifier">U</span> <span class="special">&&</span></code> |
| is not convertible to <code class="computeroutput"><span class="identifier">T</span></code>, |
| the program is ill-formed. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> On compilers that do not support |
| ref-qualifiers on member functions this overload is replaced with the |
| <code class="computeroutput"><span class="keyword">const</span></code>-qualified member |
| function. On compilers without rvalue reference support the type of |
| <code class="computeroutput"><span class="identifier">v</span></code> becomes <code class="computeroutput"><span class="identifier">U</span> <span class="keyword">const</span><span class="special">&</span></code>. |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_value_or_move"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="identifier">T</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value_or</span><span class="special">(</span><span class="identifier">U</span> <span class="special">&&</span> |
| <span class="identifier">v</span><span class="special">)</span> |
| <span class="special">&&</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">if</span> <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(**</span><span class="keyword">this</span><span class="special">);</span> <span class="keyword">else</span> <span class="keyword">return</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special"><</span><span class="identifier">U</span><span class="special">>(</span><span class="identifier">v</span><span class="special">);</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Remarks:</strong></span> If <code class="computeroutput"><span class="identifier">T</span></code> |
| is not <code class="computeroutput"><span class="identifier">MoveConstructible</span></code> |
| or <code class="computeroutput"><span class="identifier">U</span> <span class="special">&&</span></code> |
| is not convertible to <code class="computeroutput"><span class="identifier">T</span></code>, |
| the program is ill-formed. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> On compilers that do not support |
| ref-qualifiers on member functions this overload is not present. |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_value_or_call"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="identifier">T</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value_or_eval</span><span class="special">(</span><span class="identifier">F</span> <span class="identifier">f</span><span class="special">)</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code> |
| is <a href="../../../../../../utility/CopyConstructible.html" target="_top"><code class="computeroutput"><span class="identifier">CopyConstructible</span></code></a> and <code class="computeroutput"><span class="identifier">F</span></code> models a <a href="http://www.sgi.com/tech/stl/Generator.html" target="_top"><code class="computeroutput"><span class="identifier">Generator</span></code></a> whose result type |
| is convertible to <code class="computeroutput"><span class="identifier">T</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Effects:</strong></span> <code class="computeroutput"><span class="keyword">if</span> |
| <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="special">**</span><span class="keyword">this</span><span class="special">;</span> <span class="keyword">else</span> <span class="keyword">return</span> <span class="identifier">f</span><span class="special">();</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> On compilers that do not support |
| ref-qualifiers on member functions this overload is replaced with the |
| <code class="computeroutput"><span class="keyword">const</span></code>-qualified member |
| function. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="keyword">int</span> <span class="identifier">complain_and_0</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="identifier">clog</span> <span class="special"><<</span> <span class="string">"no value returned, using default"</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span> |
| <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> |
| <span class="special">}</span> |
| |
| <span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">o1</span> <span class="special">=</span> <span class="number">1</span><span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">oN</span> <span class="special">=</span> <span class="identifier">none</span><span class="special">;</span> |
| |
| <span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="identifier">o1</span><span class="special">.</span><span class="identifier">value_or_eval</span><span class="special">(</span><span class="identifier">complain_and_0</span><span class="special">);</span> <span class="comment">// fun not called</span> |
| <span class="identifier">assert</span> <span class="special">(</span><span class="identifier">i</span> <span class="special">==</span> <span class="number">1</span><span class="special">);</span> |
| |
| <span class="keyword">int</span> <span class="identifier">j</span> <span class="special">=</span> <span class="identifier">oN</span><span class="special">.</span><span class="identifier">value_or_eval</span><span class="special">(</span><span class="identifier">complain_and_0</span><span class="special">);</span> <span class="comment">// fun called</span> |
| <span class="identifier">assert</span> <span class="special">(</span><span class="identifier">i</span> <span class="special">==</span> <span class="number">0</span><span class="special">);</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_value_or_call_move"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="identifier">T</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value_or_eval</span><span class="special">(</span><span class="identifier">F</span> <span class="identifier">f</span><span class="special">)</span> <span class="special">&&</span> |
| <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code> |
| is <code class="computeroutput"><span class="identifier">MoveConstructible</span></code> |
| and <code class="computeroutput"><span class="identifier">F</span></code> models a <a href="http://www.sgi.com/tech/stl/Generator.html" target="_top"><code class="computeroutput"><span class="identifier">Generator</span></code></a> |
| whose result type is convertible to <code class="computeroutput"><span class="identifier">T</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Effects:</strong></span> <code class="computeroutput"><span class="keyword">if</span> |
| <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(**</span><span class="keyword">this</span><span class="special">);</span> <span class="keyword">else</span> <span class="keyword">return</span> |
| <span class="identifier">f</span><span class="special">();</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> On compilers that do not support |
| ref-qualifiers on member functions this overload is not present. |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_get_value_or_value"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> |
| <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get_value_or</span><span class="special">(</span> |
| <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="keyword">default</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get_value_or</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&</span> <span class="keyword">default</span> |
| <span class="special">)</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span> |
| <span class="keyword">const</span><span class="special">&</span> |
| <span class="identifier">get_optional_value_or</span> <span class="special">(</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">o</span><span class="special">,</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="keyword">default</span> <span class="special">)</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">get_optional_value_or</span> |
| <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> |
| <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>&</span> |
| <span class="identifier">o</span><span class="special">,</span> |
| <span class="identifier">T</span><span class="special">&</span> |
| <span class="keyword">default</span> <span class="special">)</span> |
| <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Deprecated:</strong></span> Use <code class="computeroutput"><span class="identifier">value_or</span><span class="special">()</span></code> instead. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Returns:</strong></span> A reference to the contained |
| value, if any, or <code class="computeroutput"><span class="keyword">default</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Throws:</strong></span> Nothing. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">,</span> <span class="identifier">z</span> <span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span><span class="special">;</span> |
| <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">=</span> <span class="identifier">def</span><span class="special">.</span><span class="identifier">get_value_or</span><span class="special">(</span><span class="identifier">z</span><span class="special">);</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">y</span> <span class="special">==</span> <span class="identifier">z</span> <span class="special">)</span> <span class="special">;</span> |
| |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">(</span> <span class="identifier">v</span> <span class="special">);</span> |
| <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">u</span> <span class="special">=</span> <span class="identifier">get_optional_value_or</span><span class="special">(</span><span class="identifier">opt</span><span class="special">,</span><span class="identifier">z</span><span class="special">);</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">u</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">u</span> <span class="special">!=</span> <span class="identifier">z</span> <span class="special">)</span> <span class="special">;</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_get_ptr"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> |
| <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get_ptr</span><span class="special">()</span> |
| <span class="keyword">const</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">T</span><span class="special">*</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get_ptr</span><span class="special">()</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span> |
| <span class="keyword">const</span><span class="special">*</span> |
| <span class="identifier">get_pointer</span> <span class="special">(</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span><span class="special">*</span> <span class="identifier">get_pointer</span> |
| <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> |
| <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span> |
| <span class="special">&)</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Returns:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized, a pointer to the |
| contained value; else <code class="computeroutput"><span class="number">0</span></code> |
| (<span class="emphasis"><em>null</em></span>). |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Throws:</strong></span> Nothing. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> The contained value is permanently |
| stored within <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>, |
| so you should not hold nor delete this pointer |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span> <span class="identifier">copt</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span> |
| <span class="identifier">T</span><span class="special">*</span> <span class="identifier">p</span> <span class="special">=</span> <span class="identifier">opt</span><span class="special">.</span><span class="identifier">get_ptr</span><span class="special">()</span> <span class="special">;</span> |
| <span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">cp</span> <span class="special">=</span> <span class="identifier">copt</span><span class="special">.</span><span class="identifier">get_ptr</span><span class="special">();</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">p</span> <span class="special">==</span> <span class="identifier">get_pointer</span><span class="special">(</span><span class="identifier">opt</span><span class="special">)</span> <span class="special">);</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">cp</span> <span class="special">==</span> <span class="identifier">get_pointer</span><span class="special">(</span><span class="identifier">copt</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_operator_arrow"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> |
| <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span> <span class="special">->()</span> |
| <span class="keyword">const</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">T</span><span class="special">*</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span> |
| <span class="special">->()</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Requires: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Returns:</strong></span> A pointer to the contained |
| value. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Throws:</strong></span> Nothing. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> The requirement is asserted |
| via <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">X</span> <span class="special">{</span> <span class="keyword">int</span> <span class="identifier">mdata</span> <span class="special">;</span> <span class="special">}</span> <span class="special">;</span> |
| <span class="identifier">X</span> <span class="identifier">x</span> <span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">X</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">(</span><span class="identifier">x</span><span class="special">);</span> |
| <span class="identifier">opt</span><span class="special">-></span><span class="identifier">mdata</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_operator_bool"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span> |
| <span class="keyword">bool</span><span class="special">()</span> |
| <span class="keyword">const</span> <span class="keyword">noexcept</span> |
| <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="identifier">get_ptr</span><span class="special">()</span> <span class="special">!=</span> <span class="number">0</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> On compilers that do not support |
| explicit conversion operators this falls back to safe-bool idiom. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">def</span> <span class="special">==</span> <span class="number">0</span> <span class="special">);</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">(</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt</span> <span class="special">);</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt</span> <span class="special">!=</span> <span class="number">0</span> <span class="special">);</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_operator_not"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">bool</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">!()</span> <span class="keyword">noexcept</span> |
| <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Returns:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is uninitialized, <code class="computeroutput"><span class="keyword">true</span></code>; else <code class="computeroutput"><span class="keyword">false</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> This operator is provided for |
| those compilers which can't use the <span class="emphasis"><em>unspecified-bool-type |
| operator</em></span> in certain boolean contexts. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">opt</span> <span class="special">);</span> |
| <span class="special">*</span><span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">some_T</span> <span class="special">;</span> |
| |
| <span class="comment">// Notice the "double-bang" idiom here.</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">!!</span><span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_is_initialized"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">bool</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">is_initialized</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> |
| <span class="bold"><strong>Deprecated:</strong></span> Same as <code class="computeroutput"><span class="keyword">explicit</span> <span class="keyword">operator</span> |
| <span class="keyword">bool</span> <span class="special">()</span> |
| <span class="special">;</span></code> |
| </li></ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <h6> |
| <a name="boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics.h1"></a> |
| <span class="phrase"><a name="boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics.free_functions"></a></span><a class="link" href="detailed_semantics.html#boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics.free_functions">Free |
| functions</a> |
| </h6> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_make_optional_value"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span> <span class="identifier">make_optional</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="identifier">v</span><span class="special">)</span></code> for the <span class="emphasis"><em>deduced</em></span> |
| type <code class="computeroutput"><span class="identifier">T</span></code> of <code class="computeroutput"><span class="identifier">v</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span> <span class="keyword">void</span> <span class="identifier">foo</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span> |
| |
| <span class="identifier">foo</span> <span class="special">(</span> <span class="identifier">make_optional</span><span class="special">(</span><span class="number">1</span><span class="special">+</span><span class="number">1</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> <span class="comment">// Creates an optional<int></span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_make_optional_bool_value"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span> <span class="identifier">make_optional</span><span class="special">(</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> |
| <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="identifier">condition</span><span class="special">,</span><span class="identifier">v</span><span class="special">)</span></code> for the <span class="emphasis"><em>deduced</em></span> |
| type <code class="computeroutput"><span class="identifier">T</span></code> of <code class="computeroutput"><span class="identifier">v</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">calculate_foo</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="keyword">double</span> <span class="identifier">val</span> <span class="special">=</span> <span class="identifier">compute_foo</span><span class="special">();</span> |
| <span class="keyword">return</span> <span class="identifier">make_optional</span><span class="special">(</span><span class="identifier">is_not_nan_and_finite</span><span class="special">(</span><span class="identifier">val</span><span class="special">),</span><span class="identifier">val</span><span class="special">);</span> |
| <span class="special">}</span> |
| |
| <span class="identifier">optional</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">v</span> <span class="special">=</span> <span class="identifier">calculate_foo</span><span class="special">();</span> |
| <span class="keyword">if</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">v</span> <span class="special">)</span> |
| <span class="identifier">error</span><span class="special">(</span><span class="string">"foo wasn't computed"</span><span class="special">);</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_operator_compare_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span> |
| <span class="special">==</span> <span class="special">(</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code> |
| shall meet requirements of <a href="http://www.sgi.com/tech/stl/EqualityComparable.html" target="_top"><code class="computeroutput"><span class="identifier">EqualityComparable</span></code></a>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Returns:</strong></span> If both <code class="computeroutput"><span class="identifier">x</span></code> |
| and <code class="computeroutput"><span class="identifier">y</span></code> are initialized, |
| <code class="computeroutput"><span class="special">(*</span><span class="identifier">x</span> |
| <span class="special">==</span> <span class="special">*</span><span class="identifier">y</span><span class="special">)</span></code>. |
| If only <code class="computeroutput"><span class="identifier">x</span></code> or <code class="computeroutput"><span class="identifier">y</span></code> is initialized, <code class="computeroutput"><span class="keyword">false</span></code>. |
| If both are uninitialized, <code class="computeroutput"><span class="keyword">true</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> This definition guarantees |
| that <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> |
| not containing a value is compared unequal to any <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> containing any value, and equal |
| to any other <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> not containing a value. Pointers |
| have shallow relational operators while <code class="computeroutput"><span class="identifier">optional</span></code> |
| has deep relational operators. Do not use <code class="computeroutput"><span class="keyword">operator</span><span class="special">==</span></code> directly in generic code which expect |
| to be given either an <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> or a pointer; use <a href="../../../../../../utility/OptionalPointee.html#equal" target="_top"><code class="computeroutput"><span class="identifier">equal_pointees</span><span class="special">()</span></code></a> |
| instead |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">oN</span><span class="special">,</span> <span class="identifier">oN_</span><span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">o1</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">1</span><span class="special">)),</span> <span class="identifier">o1_</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">1</span><span class="special">));</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">o2</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">));</span> |
| |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">oN</span> <span class="special">==</span> <span class="identifier">oN</span> <span class="special">);</span> <span class="comment">// Identity implies equality</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span> <span class="special">==</span> <span class="identifier">o1</span> <span class="special">);</span> <span class="comment">//</span> |
| |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">oN</span> <span class="special">==</span> <span class="identifier">oN_</span> <span class="special">);</span> <span class="comment">// Both uninitialized compare equal</span> |
| |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">oN</span> <span class="special">!=</span> <span class="identifier">o1</span> <span class="special">);</span> <span class="comment">// Initialized unequal to initialized.</span> |
| |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span> <span class="special">==</span> <span class="identifier">o1_</span> <span class="special">);</span> <span class="comment">// Both initialized compare as (*lhs == *rhs)</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span> <span class="special">!=</span> <span class="identifier">o2</span> <span class="special">);</span> <span class="comment">//</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_operator_compare_less_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span> |
| <span class="special"><</span> <span class="special">(</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Requires:</strong></span> Expression <code class="computeroutput"><span class="special">*</span><span class="identifier">x</span> <span class="special"><</span> <span class="special">*</span><span class="identifier">y</span></code> shall be well-formed and its result |
| shall be convertible to <code class="computeroutput"><span class="keyword">bool</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">(!</span><span class="identifier">y</span><span class="special">)</span> <span class="special">?</span> <span class="keyword">false</span> <span class="special">:</span> <span class="special">(!</span><span class="identifier">x</span><span class="special">)</span> <span class="special">?</span> <span class="keyword">true</span> <span class="special">:</span> <span class="special">*</span><span class="identifier">x</span> <span class="special"><</span> |
| <span class="special">*</span><span class="identifier">y</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> This definition guarantees |
| that <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> |
| not containing a value is ordered as less than any <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> containing any value, and equivalent |
| to any other <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> not containing a value. Pointers |
| have shallow relational operators while <code class="computeroutput"><span class="identifier">optional</span></code> |
| has deep relational operators. Do not use <code class="computeroutput"><span class="keyword">operator</span><span class="special"><</span></code> directly in generic code which |
| expect to be given either an <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> or a pointer; use <a href="../../../../../../utility/OptionalPointee.html#less" target="_top"><code class="computeroutput"><span class="identifier">less_pointees</span><span class="special">()</span></code></a> |
| instead. <code class="computeroutput"><span class="identifier">T</span></code> need not |
| be <a href="http://www.sgi.com/tech/stl/LessThanComparable.html" target="_top"><code class="computeroutput"><span class="identifier">LessThanComparable</span></code></a>. Only |
| single <code class="computeroutput"><span class="keyword">operator</span><span class="special"><</span></code> |
| is required. Other relational operations are defined in terms of this |
| one. If <code class="computeroutput"><span class="identifier">T</span></code>'s <code class="computeroutput"><span class="keyword">operator</span><span class="special"><</span></code> |
| satisfies the axioms of <a href="http://www.sgi.com/tech/stl/LessThanComparable.html" target="_top"><code class="computeroutput"><span class="identifier">LessThanComparable</span></code></a> (transitivity, |
| antisymmetry and irreflexivity), <code class="computeroutput"><span class="identifier">optinal</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> is <a href="http://www.sgi.com/tech/stl/LessThanComparable.html" target="_top"><code class="computeroutput"><span class="identifier">LessThanComparable</span></code></a>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">oN</span><span class="special">,</span> <span class="identifier">oN_</span><span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">o0</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">0</span><span class="special">));</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">o1</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">1</span><span class="special">));</span> |
| |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">oN</span> <span class="special"><</span> <span class="identifier">oN</span><span class="special">)</span> <span class="special">);</span> <span class="comment">// Identity implies equivalence</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">o1</span> <span class="special"><</span> <span class="identifier">o1</span><span class="special">)</span> <span class="special">);</span> |
| |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">oN</span> <span class="special"><</span> <span class="identifier">oN_</span><span class="special">)</span> <span class="special">);</span> <span class="comment">// Two uninitialized are equivalent</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">oN_</span> <span class="special"><</span> <span class="identifier">oN</span><span class="special">)</span> <span class="special">);</span> |
| |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">oN</span> <span class="special"><</span> <span class="identifier">o0</span> <span class="special">);</span> <span class="comment">// Uninitialized is less than initialized</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">o0</span> <span class="special"><</span> <span class="identifier">oN</span><span class="special">)</span> <span class="special">);</span> |
| |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span> <span class="special"><</span> <span class="identifier">o2</span> <span class="special">)</span> <span class="special">;</span> <span class="comment">// Two initialized compare as (*lhs < *rhs)</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">o2</span> <span class="special"><</span> <span class="identifier">o1</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">o2</span> <span class="special"><</span> <span class="identifier">o2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> |
| </pre> |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_operator_compare_not_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span> |
| <span class="special">!=</span> <span class="special">(</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> |
| <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span> |
| <span class="identifier">x</span> <span class="special">==</span> |
| <span class="identifier">y</span> <span class="special">);</span></code> |
| </li></ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_operator_compare_greater_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span> |
| <span class="special">></span> <span class="special">(</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> |
| <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">(</span> |
| <span class="identifier">y</span> <span class="special"><</span> |
| <span class="identifier">x</span> <span class="special">);</span></code> |
| </li></ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_operator_compare_less_or_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span> |
| <span class="special"><=</span> <span class="special">(</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> |
| <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span> |
| <span class="identifier">y</span> <span class="special"><</span> |
| <span class="identifier">x</span> <span class="special">);</span></code> |
| </li></ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_operator_compare_greater_or_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span> |
| <span class="special">>=</span> <span class="special">(</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> |
| <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span> |
| <span class="identifier">x</span> <span class="special"><</span> |
| <span class="identifier">y</span> <span class="special">);</span></code> |
| </li></ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_operator_compare_equal_optional_none"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span> |
| <span class="special">==</span> <span class="special">(</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">none_t</span> <span class="special">)</span> |
| <span class="keyword">noexcept</span><span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span> |
| <span class="special">==</span> <span class="special">(</span> |
| <span class="identifier">none_t</span><span class="special">,</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span> <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">!</span><span class="identifier">x</span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code> |
| need not meet requirements of <a href="http://www.sgi.com/tech/stl/EqualityComparable.html" target="_top"><code class="computeroutput"><span class="identifier">EqualityComparable</span></code></a>. |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_operator_compare_not_equal_optional_none"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span> |
| <span class="special">!=</span> <span class="special">(</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">none_t</span> <span class="special">)</span> |
| <span class="keyword">noexcept</span><span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span> |
| <span class="special">!=</span> <span class="special">(</span> |
| <span class="identifier">none_t</span><span class="special">,</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span> <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> |
| <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span> |
| <span class="identifier">x</span> <span class="special">==</span> |
| <span class="identifier">y</span> <span class="special">);</span></code> |
| </li></ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_swap_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> |
| <code class="computeroutput"><span class="keyword">void</span> <span class="identifier">swap</span> |
| <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span> <span class="identifier">y</span> |
| <span class="special">)</span> <span class="special">;</span></code> |
| </p></blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>Requires:</strong></span> Lvalues of type <code class="computeroutput"><span class="identifier">T</span></code> shall be swappable and <code class="computeroutput"><span class="identifier">T</span></code> shall be <code class="computeroutput"><span class="identifier">MoveConstructible</span></code>. |
| </li> |
| <li class="listitem"> |
| <p class="simpara"> |
| <span class="bold"><strong>Effects:</strong></span> |
| </p> |
| <div class="informaltable"><table class="table"> |
| <colgroup> |
| <col> |
| <col> |
| <col> |
| </colgroup> |
| <thead><tr> |
| <th> |
| </th> |
| <th> |
| <p> |
| <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> |
| contains a value |
| </p> |
| </th> |
| <th> |
| <p> |
| <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> |
| does not contain a value |
| </p> |
| </th> |
| </tr></thead> |
| <tbody> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="identifier">rhs</span></code> contains |
| a value |
| </p> |
| </td> |
| <td> |
| <p> |
| calls <code class="computeroutput"><span class="identifier">swap</span><span class="special">(*(*</span><span class="keyword">this</span><span class="special">),</span> <span class="special">*</span><span class="identifier">rhs</span><span class="special">)</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| initializes the contained value of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> as if direct-initializing |
| an object of type <code class="computeroutput"><span class="identifier">T</span></code> |
| with the expression <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code>, followed by <code class="computeroutput"><span class="identifier">rhs</span><span class="special">.</span><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>, |
| <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> |
| contains a value and <code class="computeroutput"><span class="identifier">rhs</span></code> |
| does not contain a value |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="identifier">rhs</span></code> does |
| not contain a value |
| </p> |
| </td> |
| <td> |
| <p> |
| initializes the contained value of <code class="computeroutput"><span class="identifier">rhs</span></code> |
| as if direct-initializing an object of type <code class="computeroutput"><span class="identifier">T</span></code> with the expression |
| <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*(*</span><span class="keyword">this</span><span class="special">))</span></code>, |
| followed by <code class="computeroutput"><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value |
| and <code class="computeroutput"><span class="identifier">rhs</span></code> contains |
| a value |
| </p> |
| </td> |
| <td> |
| <p> |
| no effect |
| </p> |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Postconditions:</strong></span> The states of <code class="computeroutput"><span class="identifier">x</span></code> and <code class="computeroutput"><span class="identifier">y</span></code> |
| interchanged. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Throws:</strong></span> If both are initialized, whatever |
| <code class="computeroutput"><span class="identifier">swap</span><span class="special">(</span><span class="identifier">T</span><span class="special">&,</span><span class="identifier">T</span><span class="special">&)</span></code> |
| throws. If only one is initialized, whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">)</span></code> |
| throws. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Example:</strong></span> |
| <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">(</span><span class="number">12</span><span class="special">);</span> |
| <span class="identifier">T</span> <span class="identifier">y</span><span class="special">(</span><span class="number">21</span><span class="special">);</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def0</span> <span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def1</span> <span class="special">;</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">optX</span><span class="special">(</span><span class="identifier">x</span><span class="special">);</span> |
| <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">optY</span><span class="special">(</span><span class="identifier">y</span><span class="special">);</span> |
| |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">def0</span><span class="special">,</span><span class="identifier">def1</span><span class="special">);</span> <span class="comment">// no-op</span> |
| |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">def0</span><span class="special">,</span><span class="identifier">optX</span><span class="special">);</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def0</span> <span class="special">==</span> <span class="identifier">x</span> <span class="special">);</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">optX</span> <span class="special">);</span> |
| |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">def0</span><span class="special">,</span><span class="identifier">optX</span><span class="special">);</span> <span class="comment">// Get back to original values</span> |
| |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">optX</span><span class="special">,</span><span class="identifier">optY</span><span class="special">);</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">optX</span> <span class="special">==</span> <span class="identifier">y</span> <span class="special">);</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">optY</span> <span class="special">==</span> <span class="identifier">x</span> <span class="special">);</span> |
| </pre> |
| </li> |
| </ul></div> |
| </div> |
| <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> |
| <td align="left"></td> |
| <td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014, 2015 Andrzej Krzemieński<p> |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) |
| </p> |
| </div></td> |
| </tr></table> |
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