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</div>
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<div class="section">
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
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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="id1059493"></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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<p>
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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
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Sequence</a> like <a class="link" href="container/list.html" title="list"><code class="computeroutput"><span class="identifier">list</span></code></a>
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is that what could have been linear runtime complexity effectively becomes
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constant O(1) due to compiler optimization of C++ inlined functions, however
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deeply recursive (up to a certain compiler limit of course). Compile time complexity
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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="id1059534"></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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Associative sequences use function overloading to implement membership testing
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and type associated key lookup. This amounts to constant runtime and amortized
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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
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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="id1059586"></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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Tag dispatching is a generic programming technique for selecting template specializations.
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There are typically 3 components involved in the tag dispatching mechanism:
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</p>
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<div class="orderedlist"><ol class="orderedlist" type="1">
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<li class="listitem">
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A type for which an appropriate template specialization is required
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</li>
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<li class="listitem">
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A metafunction that associates the type with a tag type
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</li>
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<li class="listitem">
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A template that is specialized for the tag type
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</li>
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</ol></div>
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<p>
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For example, the fusion <code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">begin</span></code> metafunction
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is implemented as follows:
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</p>
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<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>
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<span class="keyword">struct</span> <span class="identifier">begin</span>
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<span class="special">{</span>
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<span class="keyword">typedef</span> <span class="keyword">typename</span>
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<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>
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<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>
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<span class="identifier">type</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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In the case:
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</p>
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<div class="orderedlist"><ol class="orderedlist" type="1">
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<li class="listitem">
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<code class="computeroutput"><span class="identifier">Sequence</span></code> is the type for
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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>
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is required
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</li>
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<li class="listitem">
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<code class="computeroutput"><span class="identifier">traits</span><span class="special">::</span><span class="identifier">tag_of</span></code> is the metafunction that associates
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<code class="computeroutput"><span class="identifier">Sequence</span></code> with an appropriate
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tag
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</li>
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<li class="listitem">
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<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
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to provide an implementation for each tag type
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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="id1059874"></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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Unlike <a href="http://www.boost.org/libs/mpl/index.html" target="_top">MPL</a>, there
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is no extensibe sequence concept in fusion. This does not mean that Fusion
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sequences are not extensible. In fact, all Fusion sequences are inherently
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extensible. It is just that the manner of sequence extension in Fusion is diferent
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from both <a href="http://en.wikipedia.org/wiki/Standard_Template_Library" target="_top">STL</a>
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and <a href="http://www.boost.org/libs/mpl/index.html" target="_top">MPL</a> on account
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of the lazy nature of fusion <a class="link" href="algorithm.html" title="Algorithm">Algorithms</a>.
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<a href="http://en.wikipedia.org/wiki/Standard_Template_Library" target="_top">STL</a>
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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>
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sequences, on the other hand, are extended through "intrinsic" functions
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that actually return whole sequences. <a href="http://www.boost.org/libs/mpl/index.html" target="_top">MPL</a>
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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
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<code class="computeroutput"><span class="identifier">push_back</span></code> does not actually
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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
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an extended <code class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">vector</span></code>.
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</p>
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<p>
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Like <a href="http://www.boost.org/libs/mpl/index.html" target="_top">MPL</a>, Fusion
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too is purely functional and can not have side effects. With runtime efficiency
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in mind, Fusion sequences are extended through generic functions that return
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<a class="link" href="view.html" title="View">Views</a>. <a class="link" href="view.html" title="View">Views</a>
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are sequences that do not actually contain data, but instead impart an alternative
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presentation over the data from one or more underlying sequences. <a class="link" href="view.html" title="View">Views</a>
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are proxies. They provide an efficient yet purely functional way to work on
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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
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<a class="link" href="container/vector.html" title="vector"><code class="computeroutput"><span class="identifier">vector</span></code></a>.
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A <a class="link" href="view/joint_view.html" title="joint_view"><code class="computeroutput"><span class="identifier">joint_view</span></code></a>
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holds a reference to the original sequence plus the appended data --making
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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="id1060057"></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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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
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to something suitable to be stored as a sequence element. In general, the element
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types are stored as plain values. Example:
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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="number">1</span><span class="special">,</span> <span class="char">'x'</span><span class="special">)</span>
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</pre>
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<p>
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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>
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<span class="keyword">char</span><span class="special">></span></code>.
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</p>
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<p>
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There are a few exceptions, however.
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</p>
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<p>
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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="id1060161" href="#ftn.id1060161" 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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<p>
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creates a <a class="link" href="container/list.html" title="list"><code class="computeroutput"><span class="identifier">list</span></code></a>
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of type
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</p>
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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">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>
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</pre>
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<p>
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<span class="bold"><strong>Function pointers:</strong></span>
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</p>
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<p>
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Function pointers are deduced to the plain non-reference type (i.e. to plain
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function pointer). Example:
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</p>
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<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>
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<span class="special">...</span>
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<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>
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</pre>
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<p>
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creates a <a class="link" href="container/list.html" title="list"><code class="computeroutput"><span class="identifier">list</span></code></a>
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of type
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</p>
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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="id1060448"></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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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
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types as plain non-reference types. Example:
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</p>
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<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>
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<span class="special">...</span>
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<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>
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</pre>
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<p>
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creates a <a class="link" href="container/list.html" title="list"><code class="computeroutput"><span class="identifier">list</span></code></a>
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of type
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</p>
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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="identifier">A</span><span class="special">,</span> <span class="identifier">B</span><span class="special">></span>
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</pre>
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<p>
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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>
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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
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(respectively) instead. The mechanism does not compromise const correctness
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since a const object wrapped with ref results in a tuple element with const
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reference type (see the fifth code line below). Examples:
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</p>
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<p>
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For example:
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</p>
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<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>
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<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>
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</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>
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</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&>
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</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&>
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</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&>
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</span></pre>
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<p>
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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="id1060903"></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>
|
|
<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.id1060161" href="#id1060161" 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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