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<div class="refentry" title="Struct template fold">
<a name="boost.proto.fold"></a><div class="titlepage"></div>
<div class="refnamediv">
<h2><span class="refentrytitle">Struct template fold</span></h2>
<p>boost::proto::fold — A <a class="link" href="../../PrimitiveTransform.html" title="Concept PrimitiveTransform">PrimitiveTransform</a> that invokes the
<code class="computeroutput">fusion::fold<></code> algorithm to accumulate a value.</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="emphasis"><em>// In header: <<a class="link" href="../../proto/reference.html#header.boost.proto.transform.fold_hpp" title="Header <boost/proto/transform/fold.hpp>">boost/proto/transform/fold.hpp</a>>
</em></span><span class="bold"><strong>template</strong></span><<span class="bold"><strong>typename</strong></span> Sequence, <span class="bold"><strong>typename</strong></span> State0, <span class="bold"><strong>typename</strong></span> Fun>
<span class="bold"><strong>struct</strong></span> <a class="link" href="fold.html" title="Struct template fold">fold</a> : <span class="bold"><strong></strong></span> <a class="link" href="transform.html" title="Struct template transform">proto::transform</a>< fold<Sequence, State0, Fun> > {
<span class="emphasis"><em>// member classes/structs/unions</em></span>
<span class="bold"><strong>template</strong></span><<span class="bold"><strong>typename</strong></span> Expr, <span class="bold"><strong>typename</strong></span> State, <span class="bold"><strong>typename</strong></span> Data>
<span class="bold"><strong>struct</strong></span> <a class="link" href="fold/impl.html" title="Struct template impl">impl</a> : <span class="bold"><strong></strong></span> <a class="link" href="transform_impl.html" title="Struct template transform_impl">proto::transform_impl</a>< Expr, State, Data > {
<span class="emphasis"><em>// types</em></span>
<span class="bold"><strong>typedef</strong></span> <a class="link" href="when.html" title="Struct template when">when</a><<a class="link" href="_.html" title="Struct _">_</a>, Sequence> <a class="link" href="fold/impl.html#boost.proto.fold.impl.X">X</a>; <span class="emphasis"><em>// For exposition only</em></span>
<span class="bold"><strong>typedef</strong></span> <a class="link" href="when.html" title="Struct template when">when</a><<a class="link" href="_.html" title="Struct _">_</a>, State0> <a class="link" href="fold/impl.html#boost.proto.fold.impl.Y">Y</a>; <span class="emphasis"><em>// For exposition only</em></span>
<span class="bold"><strong>typedef</strong></span> <span class="bold"><strong>typename</strong></span> boost::result_of<X(Expr, State, Data)>::type <a class="link" href="fold/impl.html#boost.proto.fold.impl.seq">seq</a>; <span class="emphasis"><em>// A Fusion sequence, for exposition only</em></span>
<span class="bold"><strong>typedef</strong></span> <span class="bold"><strong>typename</strong></span> boost::result_of<Y(Expr, State, Data)>::type <a class="link" href="fold/impl.html#boost.proto.fold.impl.state0">state0</a>; <span class="emphasis"><em>// An initial state for the fold, for exposition only</em></span>
<span class="bold"><strong>typedef</strong></span> <span class="emphasis"><em>unspecified</em></span> <a class="link" href="fold/impl.html#boost.proto.fold.impl.fun">fun</a>; <span class="emphasis"><em>// <code class="computeroutput">fun(d)(s,e) == when<_,Fun>()(e,s,d)</code></em></span>
<span class="bold"><strong>typedef</strong></span> <span class="bold"><strong>typename</strong></span> fusion::result_of::fold<seq, state0, fun>::type <a class="link" href="fold/impl.html#boost.proto.fold.impl.result_type">result_type</a>;
<span class="emphasis"><em>// <a class="link" href="fold/impl.html#id1268763-bb">public member functions</a></em></span>
<span class="type">result_type</span> <a class="link" href="fold/impl.html#id1268768-bb"><span class="bold"><strong>operator</strong></span>()</a>(<span class="bold"><strong>typename</strong></span> impl::expr_param,
<span class="bold"><strong>typename</strong></span> impl::state_param,
<span class="bold"><strong>typename</strong></span> impl::data_param) <span class="bold"><strong>const</strong></span>;
};
};</pre></div>
<div class="refsect1" title="Description">
<a name="id1669470"></a><h2>Description</h2>
<p>
For the complete description of the behavior of the <code class="computeroutput">proto::fold<></code>
transform, see the documentation for the nested <code class="computeroutput">
<a class="link" href="fold/impl.html" title="Struct template impl">proto::fold::impl<></a>
</code> class template.
</p>
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<td align="right"><div class="copyright-footer">Copyright © 2008 Eric Niebler<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>)
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