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| <div class="section"> |
| <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
| <a name="fusion.notes"></a><a class="link" href="notes.html" title="Notes">Notes</a> |
| </h2></div></div></div> |
| <a name="fusion.notes.recursive_inlined_functions"></a><h4> |
| <a name="id1096235"></a> |
| <a class="link" href="notes.html#fusion.notes.recursive_inlined_functions">Recursive Inlined |
| Functions</a> |
| </h4> |
| <p> |
| An interesting peculiarity of functions like <a class="link" href="sequence/intrinsic/functions/at.html" title="at"><code class="computeroutput"><span class="identifier">at</span></code></a> when applied to a <a class="link" href="sequence/concepts/forward_sequence.html" title="Forward Sequence">Forward |
| Sequence</a> like <a class="link" href="container/list.html" title="list"><code class="computeroutput"><span class="identifier">list</span></code></a> |
| is that what could have been linear runtime complexity effectively becomes |
| constant O(1) due to compiler optimization of C++ inlined functions, however |
| deeply recursive (up to a certain compiler limit of course). Compile time complexity |
| remains linear. |
| </p> |
| <a name="fusion.notes.overloaded_functions"></a><h4> |
| <a name="id1096276"></a> |
| <a class="link" href="notes.html#fusion.notes.overloaded_functions">Overloaded Functions</a> |
| </h4> |
| <p> |
| Associative sequences use function overloading to implement membership testing |
| and type associated key lookup. This amounts to constant runtime and amortized |
| constant compile time complexities. There is an overloaded function, <code class="computeroutput"><span class="identifier">f</span><span class="special">(</span><span class="identifier">k</span><span class="special">)</span></code>, for each key <span class="emphasis"><em>type</em></span> <code class="computeroutput"><span class="identifier">k</span></code>. The compiler chooses the appropriate function |
| given a key, <code class="computeroutput"><span class="identifier">k</span></code>. |
| </p> |
| <a name="fusion.notes.tag_dispatching"></a><h4> |
| <a name="id1096328"></a> |
| <a class="link" href="notes.html#fusion.notes.tag_dispatching">Tag Dispatching</a> |
| </h4> |
| <p> |
| Tag dispatching is a generic programming technique for selecting template specializations. |
| There are typically 3 components involved in the tag dispatching mechanism: |
| </p> |
| <div class="orderedlist"><ol class="orderedlist" type="1"> |
| <li class="listitem"> |
| A type for which an appropriate template specialization is required |
| </li> |
| <li class="listitem"> |
| A metafunction that associates the type with a tag type |
| </li> |
| <li class="listitem"> |
| A template that is specialized for the tag type |
| </li> |
| </ol></div> |
| <p> |
| For example, the fusion <code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">begin</span></code> metafunction |
| is implemented as follows: |
| </p> |
| <pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Sequence</span><span class="special">></span> |
| <span class="keyword">struct</span> <span class="identifier">begin</span> |
| <span class="special">{</span> |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> |
| <span class="identifier">result_of</span><span class="special">::</span><span class="identifier">begin_impl</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">traits</span><span class="special">::</span><span class="identifier">tag_of</span><span class="special"><</span><span class="identifier">Sequence</span><span class="special">>::</span><span class="identifier">type</span><span class="special">>::</span> |
| <span class="keyword">template</span> <span class="identifier">apply</span><span class="special"><</span><span class="identifier">Sequence</span><span class="special">>::</span><span class="identifier">type</span> |
| <span class="identifier">type</span><span class="special">;</span> |
| <span class="special">};</span> |
| </pre> |
| <p> |
| In the case: |
| </p> |
| <div class="orderedlist"><ol class="orderedlist" type="1"> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">Sequence</span></code> is the type for |
| which a suitable implementation of <code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">begin_impl</span></code> |
| is required |
| </li> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">traits</span><span class="special">::</span><span class="identifier">tag_of</span></code> is the metafunction that associates |
| <code class="computeroutput"><span class="identifier">Sequence</span></code> with an appropriate |
| tag |
| </li> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">begin_impl</span></code> is the template which is specialized |
| to provide an implementation for each tag type |
| </li> |
| </ol></div> |
| <a name="fusion.notes.extensibility"></a><h4> |
| <a name="id1096616"></a> |
| <a class="link" href="notes.html#fusion.notes.extensibility">Extensibility</a> |
| </h4> |
| <p> |
| Unlike <a href="http://www.boost.org/libs/mpl/index.html" target="_top">MPL</a>, there |
| is no extensibe sequence concept in fusion. This does not mean that Fusion |
| sequences are not extensible. In fact, all Fusion sequences are inherently |
| extensible. It is just that the manner of sequence extension in Fusion is diferent |
| from both <a href="http://en.wikipedia.org/wiki/Standard_Template_Library" target="_top">STL</a> |
| and <a href="http://www.boost.org/libs/mpl/index.html" target="_top">MPL</a> on account |
| of the lazy nature of fusion <a class="link" href="algorithm.html" title="Algorithm">Algorithms</a>. |
| <a href="http://en.wikipedia.org/wiki/Standard_Template_Library" target="_top">STL</a> |
| containers extend themselves in place though member functions such as <a class="link" href="algorithm/transformation/functions/push_back.html" title="push_back"><code class="computeroutput"><span class="identifier">push_back</span></code></a> and <a class="link" href="algorithm/transformation/functions/insert.html" title="insert"><code class="computeroutput"><span class="identifier">insert</span></code></a>. <a href="http://www.boost.org/libs/mpl/index.html" target="_top">MPL</a> |
| sequences, on the other hand, are extended through "intrinsic" functions |
| that actually return whole sequences. <a href="http://www.boost.org/libs/mpl/index.html" target="_top">MPL</a> |
| is purely functional and can not have side effects. For example, <a href="http://www.boost.org/libs/mpl/index.html" target="_top">MPL</a>'s |
| <code class="computeroutput"><span class="identifier">push_back</span></code> does not actually |
| mutate an <code class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">vector</span></code>. It can't do that. Instead, it returns |
| an extended <code class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">vector</span></code>. |
| </p> |
| <p> |
| Like <a href="http://www.boost.org/libs/mpl/index.html" target="_top">MPL</a>, Fusion |
| too is purely functional and can not have side effects. With runtime efficiency |
| in mind, Fusion sequences are extended through generic functions that return |
| <a class="link" href="view.html" title="View">Views</a>. <a class="link" href="view.html" title="View">Views</a> |
| are sequences that do not actually contain data, but instead impart an alternative |
| presentation over the data from one or more underlying sequences. <a class="link" href="view.html" title="View">Views</a> |
| are proxies. They provide an efficient yet purely functional way to work on |
| potentially expensive sequence operations. For example, given a <a class="link" href="container/vector.html" title="vector"><code class="computeroutput"><span class="identifier">vector</span></code></a>, Fusion's <a class="link" href="algorithm/transformation/functions/push_back.html" title="push_back"><code class="computeroutput"><span class="identifier">push_back</span></code></a> returns a <a class="link" href="view/joint_view.html" title="joint_view"><code class="computeroutput"><span class="identifier">joint_view</span></code></a>, instead of an actual extended |
| <a class="link" href="container/vector.html" title="vector"><code class="computeroutput"><span class="identifier">vector</span></code></a>. |
| A <a class="link" href="view/joint_view.html" title="joint_view"><code class="computeroutput"><span class="identifier">joint_view</span></code></a> |
| holds a reference to the original sequence plus the appended data --making |
| it very cheap to pass around. |
| </p> |
| <a name="fusion.notes.element_conversion"></a><h4> |
| <a name="id1096799"></a> |
| <a class="link" href="notes.html#fusion.notes.element_conversion">Element Conversion</a> |
| </h4> |
| <p> |
| Functions that take in elemental values to form sequences (e.g. <a class="link" href="container/generation/functions/make_list.html" title="make_list"><code class="computeroutput"><span class="identifier">make_list</span></code></a>) convert their arguments |
| to something suitable to be stored as a sequence element. In general, the element |
| types are stored as plain values. Example: |
| </p> |
| <pre class="programlisting"><a class="link" href="container/generation/functions/make_list.html" title="make_list"><code class="computeroutput"><span class="identifier">make_list</span></code></a><span class="special">(</span><span class="number">1</span><span class="special">,</span> <span class="char">'x'</span><span class="special">)</span> |
| </pre> |
| <p> |
| returns a <a class="link" href="container/list.html" title="list"><code class="computeroutput"><span class="identifier">list</span></code></a><code class="computeroutput"><span class="special"><</span><span class="keyword">int</span><span class="special">,</span> |
| <span class="keyword">char</span><span class="special">></span></code>. |
| </p> |
| <p> |
| There are a few exceptions, however. |
| </p> |
| <p> |
| <span class="bold"><strong>Arrays:</strong></span> |
| </p> |
| <p> |
| Array arguments are deduced to reference to const types. For example <sup>[<a name="id1096903" href="#ftn.id1096903" class="footnote">10</a>]</sup>: |
| </p> |
| <pre class="programlisting"><a class="link" href="container/generation/functions/make_list.html" title="make_list"><code class="computeroutput"><span class="identifier">make_list</span></code></a><span class="special">(</span><span class="string">"Donald"</span><span class="special">,</span> <span class="string">"Daisy"</span><span class="special">)</span> |
| </pre> |
| <p> |
| creates a <a class="link" href="container/list.html" title="list"><code class="computeroutput"><span class="identifier">list</span></code></a> |
| of type |
| </p> |
| <pre class="programlisting"><a class="link" href="container/list.html" title="list"><code class="computeroutput"><span class="identifier">list</span></code></a><span class="special"><</span><span class="keyword">const</span> <span class="keyword">char</span> <span class="special">(&)[</span><span class="number">7</span><span class="special">],</span> <span class="keyword">const</span> <span class="keyword">char</span> <span class="special">(&)[</span><span class="number">6</span><span class="special">]></span> |
| </pre> |
| <p> |
| <span class="bold"><strong>Function pointers:</strong></span> |
| </p> |
| <p> |
| Function pointers are deduced to the plain non-reference type (i.e. to plain |
| function pointer). Example: |
| </p> |
| <pre class="programlisting"><span class="keyword">void</span> <span class="identifier">f</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">i</span><span class="special">);</span> |
| <span class="special">...</span> |
| <a class="link" href="container/generation/functions/make_list.html" title="make_list"><code class="computeroutput"><span class="identifier">make_list</span></code></a><span class="special">(&</span><span class="identifier">f</span><span class="special">);</span> |
| </pre> |
| <p> |
| creates a <a class="link" href="container/list.html" title="list"><code class="computeroutput"><span class="identifier">list</span></code></a> |
| of type |
| </p> |
| <pre class="programlisting"><a class="link" href="container/list.html" title="list"><code class="computeroutput"><span class="identifier">list</span></code></a><span class="special"><</span><span class="keyword">void</span> <span class="special">(*)(</span><span class="keyword">int</span><span class="special">)></span> |
| </pre> |
| <a name="fusion.notes.boost__ref"></a><h4> |
| <a name="id1098419"></a> |
| <a class="link" href="notes.html#fusion.notes.boost__ref">boost::ref</a> |
| </h4> |
| <p> |
| Fusion's generation functions (e.g. <a class="link" href="container/generation/functions/make_list.html" title="make_list"><code class="computeroutput"><span class="identifier">make_list</span></code></a>) by default stores the element |
| types as plain non-reference types. Example: |
| </p> |
| <pre class="programlisting"><span class="keyword">void</span> <span class="identifier">foo</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">A</span><span class="special">&</span> <span class="identifier">a</span><span class="special">,</span> <span class="identifier">B</span><span class="special">&</span> <span class="identifier">b</span><span class="special">)</span> <span class="special">{</span> |
| <span class="special">...</span> |
| <a class="link" href="container/generation/functions/make_list.html" title="make_list"><code class="computeroutput"><span class="identifier">make_list</span></code></a><span class="special">(</span><span class="identifier">a</span><span class="special">,</span> <span class="identifier">b</span><span class="special">)</span> |
| </pre> |
| <p> |
| creates a <a class="link" href="container/list.html" title="list"><code class="computeroutput"><span class="identifier">list</span></code></a> |
| of type |
| </p> |
| <pre class="programlisting"><a class="link" href="container/list.html" title="list"><code class="computeroutput"><span class="identifier">list</span></code></a><span class="special"><</span><span class="identifier">A</span><span class="special">,</span> <span class="identifier">B</span><span class="special">></span> |
| </pre> |
| <p> |
| Sometimes the plain non-reference type is not desired. You can use <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">ref</span></code> |
| and <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">cref</span></code> to store references or const references |
| (respectively) instead. The mechanism does not compromise const correctness |
| since a const object wrapped with ref results in a tuple element with const |
| reference type (see the fifth code line below). Examples: |
| </p> |
| <p> |
| For example: |
| </p> |
| <pre class="programlisting"><span class="identifier">A</span> <span class="identifier">a</span><span class="special">;</span> <span class="identifier">B</span> <span class="identifier">b</span><span class="special">;</span> <span class="keyword">const</span> <span class="identifier">A</span> <span class="identifier">ca</span> <span class="special">=</span> <span class="identifier">a</span><span class="special">;</span> |
| <a class="link" href="container/generation/functions/make_list.html" title="make_list"><code class="computeroutput"><span class="identifier">make_list</span></code></a><span class="special">(</span><span class="identifier">cref</span><span class="special">(</span><span class="identifier">a</span><span class="special">),</span> <span class="identifier">b</span><span class="special">);</span> <span class="comment">// creates list<const A&, B> |
| </span><a class="link" href="container/generation/functions/make_list.html" title="make_list"><code class="computeroutput"><span class="identifier">make_list</span></code></a><span class="special">(</span><span class="identifier">ref</span><span class="special">(</span><span class="identifier">a</span><span class="special">),</span> <span class="identifier">b</span><span class="special">);</span> <span class="comment">// creates list<A&, B> |
| </span><a class="link" href="container/generation/functions/make_list.html" title="make_list"><code class="computeroutput"><span class="identifier">make_list</span></code></a><span class="special">(</span><span class="identifier">ref</span><span class="special">(</span><span class="identifier">a</span><span class="special">),</span> <span class="identifier">cref</span><span class="special">(</span><span class="identifier">b</span><span class="special">));</span> <span class="comment">// creates list<A&, const B&> |
| </span><a class="link" href="container/generation/functions/make_list.html" title="make_list"><code class="computeroutput"><span class="identifier">make_list</span></code></a><span class="special">(</span><span class="identifier">cref</span><span class="special">(</span><span class="identifier">ca</span><span class="special">));</span> <span class="comment">// creates list<const A&> |
| </span><a class="link" href="container/generation/functions/make_list.html" title="make_list"><code class="computeroutput"><span class="identifier">make_list</span></code></a><span class="special">(</span><span class="identifier">ref</span><span class="special">(</span><span class="identifier">ca</span><span class="special">));</span> <span class="comment">// creates list<const A&> |
| </span></pre> |
| <p> |
| See <a href="http://www.boost.org/doc/html/ref.html" target="_top">Boost.Ref</a> for |
| details. |
| </p> |
| <a name="fusion.notes.adt_attribute_proxy"></a><h4> |
| <a name="id1098874"></a> |
| <a class="link" href="notes.html#fusion.notes.adt_attribute_proxy">adt_attribute_proxy</a> |
| </h4> |
| <p> |
| To adapt arbitrary data types that do not allow direct access to their members, |
| but allow indirect access via expressions (such as invocations of get- and |
| set-methods), fusion's <code class="literal">BOOST_FUSION_ADAPT_<span class="emphasis"><em>xxx</em></span>ADT<span class="emphasis"><em>xxx</em></span></code>-family |
| (e.g. <a class="link" href="adapted/adapt_adt.html" title="BOOST_FUSION_ADAPT_ADT"><code class="computeroutput"><span class="identifier">BOOST_FUSION_ADAPT_ADT</span></code></a>) |
| may be used. To bypass the restriction of not having actual lvalues that represent |
| the elements of the fusion sequence, but rather a sequence of paired expressions |
| that access the elements, the actual return type of fusion's intrinsic sequence |
| access functions (<a class="link" href="sequence/intrinsic/functions/at.html" title="at"><code class="computeroutput"><span class="identifier">at</span></code></a>, <a class="link" href="sequence/intrinsic/functions/at_c.html" title="at_c"><code class="computeroutput"><span class="identifier">at_c</span></code></a>, <a class="link" href="sequence/intrinsic/functions/at_key.html" title="at_key"><code class="computeroutput"><span class="identifier">at_key</span></code></a>, <a class="link" href="iterator/functions/deref.html" title="deref"><code class="computeroutput"><span class="identifier">deref</span></code></a>, and <a class="link" href="iterator/functions/deref_data.html" title="deref_data"><code class="computeroutput"><span class="identifier">deref_data</span></code></a>) is a proxy type, an instance |
| of <code class="computeroutput"><span class="identifier">adt_attribute_proxy</span></code>, that |
| encapsulates these expressions. |
| </p> |
| <p> |
| <code class="computeroutput"><span class="identifier">adt_attribute_proxy</span></code> is defined |
| in the namespace <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">fusion</span><span class="special">::</span><span class="identifier">extension</span></code> and has three template arguments: |
| </p> |
| <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">fusion</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">extension</span> |
| <span class="special">{</span> |
| <span class="keyword">template</span><span class="special"><</span> |
| <span class="keyword">typename</span> <span class="identifier">Type</span> |
| <span class="special">,</span> <span class="keyword">int</span> <span class="identifier">Index</span> |
| <span class="special">,</span> <span class="keyword">bool</span> <span class="identifier">Const</span> |
| <span class="special">></span> |
| <span class="keyword">struct</span> <span class="identifier">adt_attribute_proxy</span><span class="special">;</span> |
| <span class="special">}}}</span> |
| </pre> |
| <p> |
| When adapting a class type, <code class="computeroutput"><span class="identifier">adt_attribute_proxy</span></code> |
| is specialized for every element of the adapted sequence, with <code class="computeroutput"><span class="identifier">Type</span></code> being the class type that is adapted, |
| <code class="computeroutput"><span class="identifier">Index</span></code> the 0-based indices of |
| the elements, and <code class="computeroutput"><span class="identifier">Const</span></code> both |
| <code class="computeroutput"><span class="keyword">true</span></code> and <code class="computeroutput"><span class="keyword">false</span></code>. |
| The return type of fusion's intrinsic sequence access functions for the <span class="emphasis"><em>N</em></span>th |
| element of an adapted class type <code class="computeroutput"><span class="identifier">type_name</span></code> |
| is <code class="literal">adt_attribute_proxy<type_name, <span class="emphasis"><em>N</em></span>, <span class="emphasis"><em>Const</em></span>></code>, |
| with <code class="literal"><span class="emphasis"><em>Const</em></span></code> being <code class="computeroutput"><span class="keyword">true</span></code> |
| for constant instances of <code class="computeroutput"><span class="identifier">type_name</span></code> |
| and <code class="computeroutput"><span class="keyword">false</span></code> for non-constant ones. |
| </p> |
| <div class="variablelist"> |
| <p class="title"><b>Notation</b></p> |
| <dl> |
| <dt><span class="term"><code class="computeroutput"><span class="identifier">type_name</span></code></span></dt> |
| <dd><p> |
| The type to be adapted, with M attributes |
| </p></dd> |
| <dt><span class="term"><code class="computeroutput"><span class="identifier">inst</span></code></span></dt> |
| <dd><p> |
| Object of type <code class="computeroutput"><span class="identifier">type_name</span></code> |
| </p></dd> |
| <dt><span class="term"><code class="computeroutput"><span class="identifier">const_inst</span></code></span></dt> |
| <dd><p> |
| Object of type <code class="computeroutput"><span class="identifier">type_name</span> <span class="keyword">const</span></code> |
| </p></dd> |
| <dt><span class="term"><code class="literal">(attribute_type<span class="emphasis"><em>N</em></span>, attribute_const_type<span class="emphasis"><em>N</em></span>, |
| get_expr<span class="emphasis"><em>N</em></span>, set_expr<span class="emphasis"><em>N</em></span>)</code></span></dt> |
| <dd><p> |
| Attribute descriptor of the <span class="emphasis"><em>N</em></span>th attribute of <code class="computeroutput"><span class="identifier">type_name</span></code> as passed to the adaption |
| macro, 0≤<span class="emphasis"><em>N</em></span><M |
| </p></dd> |
| <dt><span class="term"><code class="literal">proxy_type<span class="emphasis"><em>N</em></span></code></span></dt> |
| <dd><p> |
| <code class="literal">adt_attribute_proxy<type_name, <span class="emphasis"><em>N</em></span>, <code class="computeroutput"><span class="keyword">false</span></code>></code> with <span class="emphasis"><em>N</em></span> |
| being an integral constant, 0≤<span class="emphasis"><em>N</em></span><M |
| </p></dd> |
| <dt><span class="term"><code class="literal">const_proxy_type<span class="emphasis"><em>N</em></span></code></span></dt> |
| <dd><p> |
| <code class="literal">adt_attribute_proxy<type_name, <span class="emphasis"><em>N</em></span>, <code class="computeroutput"><span class="keyword">true</span></code>></code> with <span class="emphasis"><em>N</em></span> |
| being an integral constant, 0≤<span class="emphasis"><em>N</em></span><M |
| </p></dd> |
| <dt><span class="term"><code class="literal">proxy<span class="emphasis"><em>N</em></span></code></span></dt> |
| <dd><p> |
| Object of type <code class="literal">proxy_type<span class="emphasis"><em>N</em></span></code> |
| </p></dd> |
| <dt><span class="term"><code class="literal">const_proxy<span class="emphasis"><em>N</em></span></code></span></dt> |
| <dd><p> |
| Object of type <code class="literal">const_proxy_type<span class="emphasis"><em>N</em></span></code> |
| </p></dd> |
| </dl> |
| </div> |
| <p> |
| <span class="bold"><strong>Expression Semantics</strong></span> |
| </p> |
| <div class="informaltable"><table class="table"> |
| <colgroup> |
| <col> |
| <col> |
| </colgroup> |
| <thead><tr> |
| <th> |
| <p> |
| Expression |
| </p> |
| </th> |
| <th> |
| <p> |
| Semantics |
| </p> |
| </th> |
| </tr></thead> |
| <tbody> |
| <tr> |
| <td> |
| <p> |
| <code class="literal">proxy_type<span class="emphasis"><em>N</em></span>(inst)</code> |
| </p> |
| </td> |
| <td> |
| <p> |
| Creates an instance of <code class="literal">proxy_type<span class="emphasis"><em>N</em></span></code> |
| with underlying object <code class="computeroutput"><span class="identifier">inst</span></code> |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="literal">const_proxy_type<span class="emphasis"><em>N</em></span>(const_inst)</code> |
| </p> |
| </td> |
| <td> |
| <p> |
| Creates an instance of <code class="literal">const_proxy_type<span class="emphasis"><em>N</em></span></code> |
| with underlying object <code class="computeroutput"><span class="identifier">const_inst</span></code> |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="literal">proxy_type<span class="emphasis"><em>N</em></span>::type</code> |
| </p> |
| </td> |
| <td> |
| <p> |
| Another name for <code class="literal">attribute_type<span class="emphasis"><em>N</em></span></code> |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="literal">const_proxy_type<span class="emphasis"><em>N</em></span>::type</code> |
| </p> |
| </td> |
| <td> |
| <p> |
| Another name for <code class="literal">const_attribute_type<span class="emphasis"><em>N</em></span></code> |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="literal">proxy<span class="emphasis"><em>N</em></span>=t</code> |
| </p> |
| </td> |
| <td> |
| <p> |
| Invokes <code class="literal">set_expr<span class="emphasis"><em>N</em></span></code>, with |
| <code class="computeroutput"><span class="identifier">t</span></code> being an arbitrary |
| object. <code class="literal">set_expr<span class="emphasis"><em>N</em></span></code> may access |
| the variables named <code class="computeroutput"><span class="identifier">obj</span></code> |
| of type <code class="computeroutput"><span class="identifier">type_name</span><span class="special">&</span></code>, which represent the corresponding |
| instance of <code class="computeroutput"><span class="identifier">type_name</span></code>, |
| and <code class="computeroutput"><span class="identifier">val</span></code> of an arbitrary |
| const-qualified reference template type parameter <code class="computeroutput"><span class="identifier">Val</span></code>, |
| which represents <code class="computeroutput"><span class="identifier">t</span></code>. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="literal">proxy<span class="emphasis"><em>N</em></span>.get()</code> |
| </p> |
| </td> |
| <td> |
| <p> |
| Invokes <code class="literal">get_expr<span class="emphasis"><em>N</em></span></code> and forwards |
| its return value. <code class="literal">get_expr<span class="emphasis"><em>N</em></span></code> |
| may access the variable named <code class="computeroutput"><span class="identifier">obj</span></code> |
| of type <code class="computeroutput"><span class="identifier">type_name</span><span class="special">&</span></code> which represents the underlying |
| instance of <code class="computeroutput"><span class="identifier">type_name</span></code>. |
| <code class="literal">attribute_type<span class="emphasis"><em>N</em></span></code> may specify |
| the type that <code class="literal">get_expr<span class="emphasis"><em>N</em></span></code> denotes |
| to. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="literal">const_proxy<span class="emphasis"><em>N</em></span>.get()</code> |
| </p> |
| </td> |
| <td> |
| <p> |
| Invokes <code class="literal">get_expr<span class="emphasis"><em>N</em></span></code> and forwards |
| its return value. <code class="literal">get_expr<span class="emphasis"><em>N</em></span></code> |
| may access the variable named <code class="computeroutput"><span class="identifier">obj</span></code> |
| of type <code class="computeroutput"><span class="identifier">type_name</span> <span class="keyword">const</span><span class="special">&</span></code> |
| which represents the underlying instance of <code class="computeroutput"><span class="identifier">type_name</span></code>. |
| <code class="literal">attribute_const_type<span class="emphasis"><em>N</em></span></code> may |
| specify the type that <code class="literal">get_expr<span class="emphasis"><em>N</em></span></code> |
| denotes to. |
| </p> |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| <p> |
| Additionally, <code class="literal">proxy_type<span class="emphasis"><em>N</em></span></code> and <code class="literal">const_proxy_type<span class="emphasis"><em>N</em></span></code> |
| are copy constructible, copy assignable and implicitly convertible to <code class="literal">proxy_type<span class="emphasis"><em>N</em></span>::type</code> |
| or <code class="literal">const_proxy_type<span class="emphasis"><em>N</em></span>::type</code>. |
| </p> |
| <div class="tip"><table border="0" summary="Tip"> |
| <tr> |
| <td rowspan="2" align="center" valign="top" width="25"><img alt="[Tip]" src="../../../../../doc/src/images/tip.png"></td> |
| <th align="left">Tip</th> |
| </tr> |
| <tr><td align="left" valign="top"><p> |
| To avoid the pitfalls of the proxy type, an arbitrary class type may also |
| be adapted directly using fusion's <a class="link" href="extension.html" title="Extension">intrinsic |
| extension mechanism</a>. |
| </p></td></tr> |
| </table></div> |
| <div class="footnotes"> |
| <br><hr width="100" align="left"> |
| <div class="footnote"><p><sup>[<a name="ftn.id1096903" href="#id1096903" class="para">10</a>] </sup> |
| Note that the type of a string literal is an array of const characters, not |
| <code class="computeroutput"><span class="keyword">const</span> <span class="keyword">char</span><span class="special">*</span></code>. To get <a class="link" href="container/generation/functions/make_list.html" title="make_list"><code class="computeroutput"><span class="identifier">make_list</span></code></a> to create a <a class="link" href="container/list.html" title="list"><code class="computeroutput"><span class="identifier">list</span></code></a> with an element of a non-const |
| array type one must use the <code class="computeroutput"><span class="identifier">ref</span></code> |
| wrapper (see <a class="link" href="notes.html#fusion.notes.boost__ref"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">ref</span></code></a>). |
| </p></div> |
| </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 © 2001-2007 Joel de Guzman, Dan Marsden, Tobias |
| Schwinger<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> |
| <hr> |
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