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| <a name="boost.apply_visitor"></a><div class="titlepage"></div> |
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| <h2><span class="refentrytitle">Function apply_visitor</span></h2> |
| <p>boost::apply_visitor — Allows compile-time checked type-safe application of the |
| given visitor to the content of the given variant, ensuring that all |
| types are handled by the visitor.</p> |
| </div> |
| <h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2> |
| <div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: <<a class="link" href="../variant/reference.html#header.boost.variant.apply_visitor_hpp" title="Header <boost/variant/apply_visitor.hpp>">boost/variant/apply_visitor.hpp</a>> |
| |
| </span> |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Visitor<span class="special">,</span> <span class="keyword">typename</span> Variant<span class="special">></span> |
| <span class="keyword">typename</span> <span class="identifier">Visitor</span><span class="special">::</span><span class="identifier">result_type</span> |
| <span class="identifier">apply_visitor</span><span class="special">(</span><span class="identifier">Visitor</span> <span class="special">&</span> visitor<span class="special">,</span> <span class="identifier">Variant</span> <span class="special">&</span> operand<span class="special">)</span><span class="special">;</span> |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Visitor<span class="special">,</span> <span class="keyword">typename</span> Variant<span class="special">></span> |
| <span class="keyword">typename</span> <span class="identifier">Visitor</span><span class="special">::</span><span class="identifier">result_type</span> |
| <span class="identifier">apply_visitor</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">Visitor</span> <span class="special">&</span> visitor<span class="special">,</span> <span class="identifier">Variant</span> <span class="special">&</span> operand<span class="special">)</span><span class="special">;</span> |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> BinaryVisitor<span class="special">,</span> <span class="keyword">typename</span> Variant1<span class="special">,</span> <span class="keyword">typename</span> Variant2<span class="special">></span> |
| <span class="keyword">typename</span> <span class="identifier">BinaryVisitor</span><span class="special">::</span><span class="identifier">result_type</span> |
| <span class="identifier">apply_visitor</span><span class="special">(</span><span class="identifier">BinaryVisitor</span> <span class="special">&</span> visitor<span class="special">,</span> <span class="identifier">Variant1</span> <span class="special">&</span> operand1<span class="special">,</span> |
| <span class="identifier">Variant2</span> <span class="special">&</span> operand2<span class="special">)</span><span class="special">;</span> |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> BinaryVisitor<span class="special">,</span> <span class="keyword">typename</span> Variant1<span class="special">,</span> <span class="keyword">typename</span> Variant2<span class="special">></span> |
| <span class="keyword">typename</span> <span class="identifier">BinaryVisitor</span><span class="special">::</span><span class="identifier">result_type</span> |
| <span class="identifier">apply_visitor</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">BinaryVisitor</span> <span class="special">&</span> visitor<span class="special">,</span> <span class="identifier">Variant1</span> <span class="special">&</span> operand1<span class="special">,</span> |
| <span class="identifier">Variant2</span> <span class="special">&</span> operand2<span class="special">)</span><span class="special">;</span> |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Visitor<span class="special">></span> |
| <a class="link" href="apply_visitor_delayed_t.html" title="Class template apply_visitor_delayed_t">apply_visitor_delayed_t</a><span class="special"><</span><span class="identifier">Visitor</span><span class="special">></span> <span class="identifier">apply_visitor</span><span class="special">(</span><span class="identifier">Visitor</span> <span class="special">&</span> visitor<span class="special">)</span><span class="special">;</span></pre></div> |
| <div class="refsect1"> |
| <a name="id3085636"></a><h2>Description</h2> |
| <p>The behavior of <code class="computeroutput">apply_visitor</code> is dependent on |
| the number of arguments on which it operates (i.e., other than the |
| visitor). The function behaves as follows: |
| |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem">Overloads accepting one operand invoke the unary function |
| call operator of the given visitor on the content of the given |
| <code class="computeroutput"><a class="link" href="variant.html" title="Class template variant">variant</a></code> operand.</li> |
| <li class="listitem">Overloads accepting two operands invoke the binary |
| function call operator of the given visitor on the content of |
| the given <code class="computeroutput"><a class="link" href="variant.html" title="Class template variant">variant</a></code> |
| operands.</li> |
| <li class="listitem">The overload accepting only a visitor returns a |
| <code class="computeroutput"><a class="link" href="apply_visitor_delayed_t.html" title="Class template apply_visitor_delayed_t">generic function object</a></code> |
| that accepts either one or two arguments and invokes |
| <code class="computeroutput"><a class="link" href="apply_visitor.html" title="Function apply_visitor">apply_visitor</a></code> using |
| these arguments and <code class="computeroutput">visitor</code>, thus behaving as |
| specified above. (This behavior is particularly useful, for |
| example, when one needs to operate on each element of a sequence |
| of variant objects using a standard library |
| algorithm.)</li> |
| </ul></div> |
| |
| </p> |
| <div class="variablelist"><table border="0"> |
| <col align="left" valign="top"> |
| <tbody> |
| <tr> |
| <td><p><span class="term">Returns:</span></p></td> |
| <td>The overloads acccepting operands return the result of |
| applying the given visitor to the content of the given operands. |
| The overload accepting only a visitor return a function object, thus |
| delaying application of the visitor to any operands.</td> |
| </tr> |
| <tr> |
| <td><p><span class="term">Requires:</span></p></td> |
| <td>The given visitor must fulfill the |
| <a class="link" href="../variant/reference.html#variant.concepts.static-visitor" title="StaticVisitor"><span class="emphasis"><em>StaticVisitor</em></span></a> |
| concept requirements with respect to each of the bounded types of the |
| given <code class="computeroutput">variant</code>.</td> |
| </tr> |
| <tr> |
| <td><p><span class="term">Throws:</span></p></td> |
| <td>The overloads accepting operands throw only if the given |
| visitor throws when applied. The overload accepting only a visitor |
| will not throw. (Note, however, that the returned |
| <a class="link" href="apply_visitor_delayed_t.html" title="Class template apply_visitor_delayed_t">function object</a> |
| may throw when invoked.)</td> |
| </tr> |
| </tbody> |
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| <td align="left"></td> |
| <td align="right"><div class="copyright-footer">Copyright © 2002, 2003 Eric Friedman, Itay Maman<p>Distributed under the Boost Software License, Version 1.0. |
| (See accompanying file <code class="filename">LICENSE_1_0.txt</code> 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> |
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