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| </div> |
| <div class="section" title="Detailed Semantics"> |
| <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
| <a name="boost_optional.detailed_semantics"></a><a class="link" href="detailed_semantics.html" title="Detailed Semantics">Detailed Semantics</a> |
| </h2></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" 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" title="Note"><table border="0" summary="Note"> |
| <tr> |
| <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../doc/html/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> |
| <a name="boost_optional.detailed_semantics.optional_class_member_functions"></a><h4> |
| <a name="id560085"></a> |
| <a class="link" href="detailed_semantics.html#boost_optional.detailed_semantics.optional_class_member_functions">optional |
| class member functions</a> |
| </h4> |
| <p> |
| <span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_constructor"></a><p> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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></code> |
| </p> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" 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>Throws:</strong></span> Nothing. |
| </li> |
| <li class="listitem"> |
| Notes: 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><p> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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></code> |
| </p> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" 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>Throws:</strong></span> Nothing. |
| </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><p> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" 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 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> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" 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_bool_value"></a><p> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"> |
| If condition is true, same as: |
| </li></ul></div> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"> |
| otherwise, same as: |
| </li></ul></div> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <p> |
| <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> <span class="special">[</span><span class="error">'</span><span class="special">(</span><span class="keyword">not</span> <span class="identifier">a</span> |
| <span class="identifier">ref</span><span class="special">)]>::</span><span class="identifier">optional</span><span class="special">()</span></code> |
| </p> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_optional_constructor_optional"></a><p> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" 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 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> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" 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 reefer 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_constructor_other_optional"></a><p> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" 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_constructor_factory"></a><p> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" 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="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_value"></a><p> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" 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> |
| </p> |
| <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="keyword">const</span><span class="special">&</span> |
| <span class="identifier">rhs</span> <span class="special">)</span> |
| <span class="special">;</span></code> |
| </p> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" 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><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, is is <span class="emphasis"><em>rebound</em></span> |
| to the new object. See <a class="link" href="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_equal_optional"></a><p> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| <span class="bold"><strong>Effect:</strong></span> Assigns another <code class="computeroutput"><span class="identifier">optional</span></code> |
| to 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 <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="keyword">operator</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</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> <span class="special">)</span></code> throws. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> If both <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="identifier">rhs</span></code> |
| are initially initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s |
| <span class="emphasis"><em>assignment operator</em></span> is used. If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initially initialized but <code class="computeroutput"><span class="identifier">rhs</span></code> is uninitialized, <code class="computeroutput"><span class="identifier">T</span></code>'s |
| [destructor] is called. If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initially uninitialized but <code class="computeroutput"><span class="identifier">rhs</span></code> is initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s |
| <span class="emphasis"><em>copy constructor</em></span> is called. |
| </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 optional 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">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> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" 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 *rhs, this |
| is is <span class="emphasis"><em>rebound</em></span> to the new object. See <a class="link" href="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_equal_other_optional"></a><p> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| <span class="bold"><strong>Effect:</strong></span> Assigns another convertible optional |
| to an optional. |
| </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 <code class="computeroutput"><span class="identifier">rhs</span></code><span class="emphasis"><em>converted</em></span> |
| 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="keyword">operator</span><span class="special">=(</span> <span class="identifier">U</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">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> If both <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and rhs are initially initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s <span class="emphasis"><em>assignment operator</em></span> |
| (from <code class="computeroutput"><span class="identifier">U</span></code>) is used. If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initially |
| initialized but <code class="computeroutput"><span class="identifier">rhs</span></code> is uninitialized, |
| <code class="computeroutput"><span class="identifier">T</span></code>'s <span class="emphasis"><em>destructor</em></span> |
| is called. If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> |
| is initially uninitialized but rhs is initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s |
| <span class="emphasis"><em>converting constructor</em></span> (from <code class="computeroutput"><span class="identifier">U</span></code>) |
| is called. |
| </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 optional 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 |
| converting constructor 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">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_reset_value"></a><p> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" 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><p> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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="special">;</span></code> |
| </p> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" 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">detail</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><p> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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></code> |
| </p> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| <span class="bold"><strong>Requirements:</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> |
| <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_get_value_or_value"></a><p> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <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> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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="keyword">operator</span><span class="special">*()</span> <span class="keyword">const</span> <span class="special">;</span></code> |
| </p> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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></code> |
| </p> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| <span class="bold"><strong>Requirements: </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> |
| <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_get_ptr"></a><p> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" 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><p> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| <span class="bold"><strong>Requirements: </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><p> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <p> |
| <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> </code><span class="emphasis"><em>unspecified-bool-type</em></span><code class="computeroutput"><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span></code> |
| </p> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| <span class="bold"><strong>Returns:</strong></span> An unspecified value which if used |
| on a boolean context is equivalent to (<code class="computeroutput"><span class="identifier">get</span><span class="special">()</span> <span class="special">!=</span> <span class="number">0</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">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><p> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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="special">;</span></code> |
| </p> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" 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>Throws:</strong></span> Nothing. |
| </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><p> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| <span class="bold"><strong>Returns: </strong></span><code class="computeroutput"><span class="keyword">true</span></code> |
| if the <code class="computeroutput"><span class="identifier">optional</span></code> is initialized, |
| <code class="computeroutput"><span class="keyword">false</span></code> otherwise. |
| </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">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="identifier">is_initialized</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="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt</span><span class="special">.</span><span class="identifier">is_initialized</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="boost_optional.detailed_semantics.free_functions"></a><h4> |
| <a name="id572503"></a> |
| <a class="link" href="detailed_semantics.html#boost_optional.detailed_semantics.free_functions">Free functions</a> |
| </h4> |
| <p> |
| <span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_make_optional_value"></a><p> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" 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><p> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" 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><p> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <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>Throws:</strong></span> Nothing. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> 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">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">12</span><span class="special">);</span> |
| <span class="identifier">T</span> <span class="identifier">z</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">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">optZ</span><span class="special">(</span><span class="identifier">z</span><span class="special">);</span> |
| |
| <span class="comment">// Identity always hold |
| </span><span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">def0</span> <span class="special">==</span> <span class="identifier">def0</span> <span class="special">);</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">optX</span> <span class="special">==</span> <span class="identifier">optX</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">def0</span> <span class="special">==</span> <span class="identifier">def1</span> <span class="special">);</span> |
| |
| <span class="comment">// Only one initialized compare unequal. |
| </span><span class="identifier">assert</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">// Both initialized compare as (*lhs == *rhs) |
| </span><span class="identifier">assert</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="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">optX</span> <span class="special">!=</span> <span class="identifier">optZ</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_less_optional_optional"></a><p> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| <span class="bold"><strong>Returns:</strong></span> If <code class="computeroutput"><span class="identifier">y</span></code> |
| is not initialized, <code class="computeroutput"><span class="keyword">false</span></code>. If |
| <code class="computeroutput"><span class="identifier">y</span></code> is initialized and <code class="computeroutput"><span class="identifier">x</span></code> is not initialized, <code class="computeroutput"><span class="keyword">true</span></code>. |
| 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>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Throws:</strong></span> Nothing. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Notes:</strong></span> 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. |
| </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">34</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">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="comment">// Identity always hold |
| </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">def</span><span class="special">)</span> <span class="special">);</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">optX</span> <span class="special">==</span> <span class="identifier">optX</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">def0</span> <span class="special">==</span> <span class="identifier">def1</span> <span class="special">);</span> |
| |
| <span class="comment">// Only one initialized compare unequal. |
| </span><span class="identifier">assert</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">// Both initialized compare as (*lhs == *rhs) |
| </span><span class="identifier">assert</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="special">;</span> |
| <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">optX</span> <span class="special">!=</span> <span class="identifier">optZ</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><p> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" 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> |
| <li class="listitem"> |
| <span class="bold"><strong>Throws:</strong></span> Nothing. |
| </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><p> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" 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> |
| <li class="listitem"> |
| <span class="bold"><strong>Throws:</strong></span> Nothing. |
| </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><p> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" 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> |
| <li class="listitem"> |
| <span class="bold"><strong>Throws:</strong></span> Nothing. |
| </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><p> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" 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> |
| <li class="listitem"> |
| <span class="bold"><strong>Throws:</strong></span> Nothing. |
| </li> |
| </ul></div> |
| <p> |
| <span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span> |
| </p> |
| <a name="reference_swap_optional_optional"></a><p> |
| </p> |
| <div class="blockquote"><blockquote class="blockquote"> |
| <p> |
| </p> |
| <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></code> |
| </p> |
| <p> |
| </p> |
| </blockquote></div> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| <span class="bold"><strong>Effect:</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, calls |
| <code class="computeroutput"><span class="identifier">swap</span><span class="special">(*</span><span class="identifier">x</span><span class="special">,*</span><span class="identifier">y</span><span class="special">)</span></code> using <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">swap</span></code>. |
| If only one is initialized, say <code class="computeroutput"><span class="identifier">x</span></code>, |
| calls: <code class="computeroutput"><span class="identifier">y</span><span class="special">.</span><span class="identifier">reset</span><span class="special">(*</span><span class="identifier">x</span><span class="special">);</span> <span class="identifier">x</span><span class="special">.</span><span class="identifier">reset</span><span class="special">();</span></code> If none is initialized, does nothing. |
| </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="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 both are initialized, <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> is used unqualified but with <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">swap</span></code> |
| introduced in scope. If only one is initialized, <code class="computeroutput"><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code> |
| and <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> If both are initialized, |
| this operation has the exception safety guarantees of <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>. |
| If only one is initialized, it has the same basic guarantee as <code class="computeroutput"><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="identifier">T</span> <span class="keyword">const</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">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<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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