<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> <title>Function apply_visitor</title> <link rel="stylesheet" href="../../../doc/src/boostbook.css" type="text/css"> <meta name="generator" content="DocBook XSL Stylesheets V1.75.2"> <link rel="home" href="../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset"> <link rel="up" href="../variant/reference.html#header.boost.variant.apply_visitor_hpp" title="Header <boost/variant/apply_visitor.hpp>"> <link rel="prev" href="apply_visitor_delayed_t.html" title="Class template apply_visitor_delayed_t"> <link rel="next" href="bad_get.html" title="Class bad_get"> </head> <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> <table cellpadding="2" width="100%"><tr> <td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../boost.png"></td> <td align="center"><a href="../../../index.html">Home</a></td> <td align="center"><a 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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="id3091453"></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> </table></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 © 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> </div></td> </tr></table> <hr> <div class="spirit-nav"> <a accesskey="p" href="apply_visitor_delayed_t.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../variant/reference.html#header.boost.variant.apply_visitor_hpp"><img src="../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="bad_get.html"><img src="../../../doc/src/images/next.png" alt="Next"></a> </div> </body> </html>