forked from boostorg/fusion
Fusion: BOOST_FUSION_ADAPT_ADT documentation
[SVN r65756]
This commit is contained in:
Christopher Schmidt
@ -27,7 +27,7 @@
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<a name="fusion.notes"></a><a class="link" href="notes.html" title="Notes">Notes</a>
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</h2></div></div></div>
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<a name="fusion.notes.recursive_inlined_functions"></a><h4>
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<a name="id1106468"></a>
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<a name="id1111870"></a>
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<a class="link" href="notes.html#fusion.notes.recursive_inlined_functions">Recursive Inlined
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Functions</a>
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</h4>
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@ -40,7 +40,7 @@
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remains linear.
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</p>
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<a name="fusion.notes.overloaded_functions"></a><h4>
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<a name="id1106508"></a>
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<a name="id1111911"></a>
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<a class="link" href="notes.html#fusion.notes.overloaded_functions">Overloaded Functions</a>
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</h4>
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<p>
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@ -50,7 +50,7 @@
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given a key, <code class="computeroutput"><span class="identifier">k</span></code>.
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</p>
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<a name="fusion.notes.tag_dispatching"></a><h4>
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<a name="id1106561"></a>
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<a name="id1111963"></a>
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<a class="link" href="notes.html#fusion.notes.tag_dispatching">Tag Dispatching</a>
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</h4>
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<p>
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@ -101,7 +101,7 @@
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</li>
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</ol></div>
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<a name="fusion.notes.extensibility"></a><h4>
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<a name="id1106849"></a>
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<a name="id1112251"></a>
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<a class="link" href="notes.html#fusion.notes.extensibility">Extensibility</a>
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</h4>
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<p>
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@ -136,7 +136,7 @@
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it very cheap to pass around.
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</p>
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<a name="fusion.notes.element_conversion"></a><h4>
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<a name="id1107032"></a>
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<a name="id1112434"></a>
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<a class="link" href="notes.html#fusion.notes.element_conversion">Element Conversion</a>
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</h4>
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<p>
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@ -157,7 +157,7 @@
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<span class="bold"><strong>Arrays:</strong></span>
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</p>
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<p>
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Array arguments are deduced to reference to const types. For example <sup>[<a name="id1107136" href="#ftn.id1107136" class="footnote">10</a>]</sup>:
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Array arguments are deduced to reference to const types. For example <sup>[<a name="id1112538" href="#ftn.id1112538" class="footnote">10</a>]</sup>:
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</p>
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<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>
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</pre>
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@ -185,7 +185,7 @@
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<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>
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</pre>
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<a name="fusion.notes.boost__ref"></a><h4>
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<a name="id1107423"></a>
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<a name="id1113932"></a>
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<a class="link" href="notes.html#fusion.notes.boost__ref">boost::ref</a>
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</h4>
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<p>
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@ -223,9 +223,241 @@
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See <a href="http://www.boost.org/doc/html/ref.html" target="_top">Boost.Ref</a> for
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details.
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</p>
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<a name="fusion.notes.adt_attribute_proxy"></a><h4>
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<a name="id1114387"></a>
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<a class="link" href="notes.html#fusion.notes.adt_attribute_proxy">adt_attribute_proxy</a>
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</h4>
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<p>
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To adapt arbitrary data types that do not allow direct access to their members,
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but allow indirect access via expressions (such as invocations of get- and
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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
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(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>)
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may be used. To bypass the restriction of not having actual lvalues that represent
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the elements of the fusion sequence, but rather a sequence of paired expressions
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that access the elements, the actual return type of fusion's intrinsic sequence
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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
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of <code class="computeroutput"><span class="identifier">adt_attribute_proxy</span></code>, that
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encapsulates these expressions.
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</p>
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<p>
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<code class="computeroutput"><span class="identifier">adt_attribute_proxy</span></code> is defined
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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:
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</p>
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<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>
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<span class="special">{</span>
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<span class="keyword">template</span><span class="special"><</span>
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<span class="keyword">typename</span> <span class="identifier">Type</span>
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<span class="special">,</span> <span class="keyword">int</span> <span class="identifier">Index</span>
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<span class="special">,</span> <span class="keyword">bool</span> <span class="identifier">Const</span>
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<span class="special">></span>
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<span class="keyword">struct</span> <span class="identifier">adt_attribute_proxy</span><span class="special">;</span>
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<span class="special">}}}</span>
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</pre>
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<p>
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When adapting a class type, <code class="computeroutput"><span class="identifier">adt_attribute_proxy</span></code>
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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,
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<code class="computeroutput"><span class="identifier">Index</span></code> the 0-based indices of
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the elements, and <code class="computeroutput"><span class="identifier">Const</span></code> both
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<code class="computeroutput"><span class="keyword">true</span></code> and <code class="computeroutput"><span class="keyword">false</span></code>.
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The return type of fusion's intrinsic sequence access functions for the <span class="emphasis"><em>N</em></span>th
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element of an adapted class type <code class="computeroutput"><span class="identifier">type_name</span></code>
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is <code class="literal">adt_attribute_proxy<type_name, <span class="emphasis"><em>N</em></span>, <span class="emphasis"><em>Const</em></span>></code>,
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with <code class="literal"><span class="emphasis"><em>Const</em></span></code> being <code class="computeroutput"><span class="keyword">true</span></code>
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for constant instances of <code class="computeroutput"><span class="identifier">type_name</span></code>
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and <code class="computeroutput"><span class="keyword">false</span></code> for non-constant ones.
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</p>
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<div class="variablelist">
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<p class="title"><b>Notation</b></p>
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<dl>
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<dt><span class="term"><code class="computeroutput"><span class="identifier">type_name</span></code></span></dt>
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<dd><p>
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The type to be adapted, with M attributes
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</p></dd>
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<dt><span class="term"><code class="computeroutput"><span class="identifier">inst</span></code></span></dt>
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<dd><p>
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Object of type <code class="computeroutput"><span class="identifier">type_name</span></code>
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</p></dd>
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<dt><span class="term"><code class="computeroutput"><span class="identifier">const_inst</span></code></span></dt>
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<dd><p>
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Object of type <code class="computeroutput"><span class="identifier">type_name</span> <span class="keyword">const</span></code>
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</p></dd>
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<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>,
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get_expr<span class="emphasis"><em>N</em></span>, set_expr<span class="emphasis"><em>N</em></span>)</code></span></dt>
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<dd><p>
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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
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macro, 0≤<span class="emphasis"><em>N</em></span><M
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</p></dd>
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<dt><span class="term"><code class="literal">proxy_type<span class="emphasis"><em>N</em></span></code></span></dt>
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<dd><p>
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<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>
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being an integral constant, 0≤<span class="emphasis"><em>N</em></span><M
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</p></dd>
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<dt><span class="term"><code class="literal">const_proxy_type<span class="emphasis"><em>N</em></span></code></span></dt>
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<dd><p>
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<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>
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being an integral constant, 0≤<span class="emphasis"><em>N</em></span><M
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</p></dd>
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<dt><span class="term"><code class="literal">proxy<span class="emphasis"><em>N</em></span></code></span></dt>
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<dd><p>
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Object of type <code class="literal">proxy_type<span class="emphasis"><em>N</em></span></code>
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</p></dd>
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<dt><span class="term"><code class="literal">const_proxy<span class="emphasis"><em>N</em></span></code></span></dt>
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<dd><p>
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Object of type <code class="literal">const_proxy_type<span class="emphasis"><em>N</em></span></code>
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</p></dd>
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</dl>
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</div>
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<p>
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<span class="bold"><strong>Expression Semantics</strong></span>
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</p>
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<div class="informaltable"><table class="table">
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<colgroup>
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<col>
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<col>
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</colgroup>
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<thead><tr>
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<th>
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<p>
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Expression
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</p>
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</th>
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<th>
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<p>
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Semantics
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</p>
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</th>
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</tr></thead>
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<tbody>
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<tr>
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<td>
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<p>
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<code class="computeroutput"><span class="identifier">proxy_type</span><span class="special">(</span><span class="identifier">inst</span><span class="special">)</span></code>
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</p>
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</td>
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<td>
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<p>
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Creates an instance of <code class="computeroutput"><span class="identifier">proxy_type</span></code>
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with underlying object <code class="computeroutput"><span class="identifier">inst</span></code>
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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<code class="computeroutput"><span class="identifier">const_proxy_type</span><span class="special">(</span><span class="identifier">const_inst</span><span class="special">)</span></code>
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</p>
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</td>
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<td>
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<p>
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Creates an instance of <code class="computeroutput"><span class="identifier">proxy_type</span></code>
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with underlying object <code class="computeroutput"><span class="identifier">const_inst</span></code>
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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<code class="computeroutput"><span class="identifier">proxy_type</span><span class="special">::</span><span class="identifier">type</span></code>
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</p>
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</td>
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<td>
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<p>
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Another name for <code class="literal">attribute_type<span class="emphasis"><em>N</em></span></code>
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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<code class="computeroutput"><span class="identifier">const_proxy_type</span><span class="special">::</span><span class="identifier">type</span></code>
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</p>
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</td>
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<td>
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<p>
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Another name for <code class="literal">const_attribute_type<span class="emphasis"><em>N</em></span></code>
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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<code class="literal">proxy<span class="emphasis"><em>N</em></span>=t</code>
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</p>
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</td>
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<td>
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<p>
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Invokes <code class="literal">set_expr<span class="emphasis"><em>N</em></span></code>, with
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<code class="computeroutput"><span class="identifier">t</span></code> being an arbitrary
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object. <code class="literal">set_expr<span class="emphasis"><em>N</em></span></code> may access
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the variables named <code class="computeroutput"><span class="identifier">obj</span></code>
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of type <code class="computeroutput"><span class="identifier">type_name</span><span class="special">&</span></code>, which represent the corresponding
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instance of <code class="computeroutput"><span class="identifier">type_name</span></code>,
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and <code class="computeroutput"><span class="identifier">val</span></code> of an arbitrary
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const-qualified reference template type parameter <code class="computeroutput"><span class="identifier">Val</span></code>,
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which represents <code class="computeroutput"><span class="identifier">t</span></code>.
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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<code class="literal">proxy<span class="emphasis"><em>N</em></span>.get()</code>
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</p>
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</td>
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<td>
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<p>
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Invokes <code class="literal">get_expr<span class="emphasis"><em>N</em></span></code> and forwards
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its return value. <code class="literal">get_expr<span class="emphasis"><em>N</em></span></code>
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may access the variable named <code class="computeroutput"><span class="identifier">obj</span></code>
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of type <code class="computeroutput"><span class="identifier">type_name</span><span class="special">&</span></code> which represents the underlying
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instance of <code class="computeroutput"><span class="identifier">type_name</span></code>.
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<code class="literal">attribute_type<span class="emphasis"><em>N</em></span></code> may specify
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the type that <code class="literal">get_expr<span class="emphasis"><em>N</em></span></code> denotes
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to.
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||||
</p>
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||||
</td>
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</tr>
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<tr>
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<td>
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<p>
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<code class="literal">const_proxy<span class="emphasis"><em>N</em></span>.get()</code>
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</p>
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</td>
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<td>
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||||
<p>
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Invokes <code class="literal">get_expr<span class="emphasis"><em>N</em></span></code> and forwards
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its return value. <code class="literal">get_expr<span class="emphasis"><em>N</em></span></code>
|
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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>
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which represents the underlying instance of <code class="computeroutput"><span class="identifier">type_name</span></code>.
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<code class="literal">attribute_const_type<span class="emphasis"><em>N</em></span></code> may
|
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specify the type that <code class="literal">get_expr<span class="emphasis"><em>N</em></span></code>
|
||||
denotes to.
|
||||
</p>
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||||
</td>
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||||
</tr>
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||||
</tbody>
|
||||
</table></div>
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||||
<p>
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||||
Additionally, <code class="computeroutput"><span class="identifier">proxy_type</span></code> and
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<code class="computeroutput"><span class="identifier">const_proxy_type</span></code> are copy constructible,
|
||||
copy assignable and implicitly convertible to <code class="computeroutput"><span class="identifier">proxy_type</span><span class="special">::</span><span class="identifier">type</span></code> or
|
||||
<code class="computeroutput"><span class="identifier">const_proxy_type</span><span class="special">::</span><span class="identifier">type</span></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.id1107136" href="#id1107136" class="para">10</a>] </sup>
|
||||
<div class="footnote"><p><sup>[<a name="ftn.id1112538" href="#id1112538" 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>
|
||||
|
||||
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