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| <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
| <a name="fusion.functional"></a><a class="link" href="functional.html" title="Functional">Functional</a> |
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| <div class="toc"><dl> |
| <dt><span class="section"><a href="functional/concepts.html">Concepts</a></span></dt> |
| <dd><dl> |
| <dt><span class="section"><a href="functional/concepts/callable.html">Callable Object</a></span></dt> |
| <dt><span class="section"><a href="functional/concepts/reg_callable.html">Regular Callable |
| Object</a></span></dt> |
| <dt><span class="section"><a href="functional/concepts/def_callable.html">Deferred Callable |
| Object</a></span></dt> |
| <dt><span class="section"><a href="functional/concepts/poly.html">Polymorphic Function |
| Object</a></span></dt> |
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| <dt><span class="section"><a href="functional/invocation.html">Invocation</a></span></dt> |
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| <dt><span class="section"><a href="functional/invocation/functions.html">Functions</a></span></dt> |
| <dt><span class="section"><a href="functional/invocation/metafunctions.html">Metafunctions</a></span></dt> |
| <dt><span class="section"><a href="functional/invocation/limits.html">Limits</a></span></dt> |
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| <dt><span class="section"><a href="functional/adapters.html">Adapters</a></span></dt> |
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| <dt><span class="section"><a href="functional/adapters/fused.html">fused</a></span></dt> |
| <dt><span class="section"><a href="functional/adapters/fused_procedure.html">fused_procedure</a></span></dt> |
| <dt><span class="section"><a href="functional/adapters/fused_function_object.html">fused_function_object</a></span></dt> |
| <dt><span class="section"><a href="functional/adapters/unfused.html">unfused</a></span></dt> |
| <dt><span class="section"><a href="functional/adapters/unfused_typed.html">unfused_typed</a></span></dt> |
| <dt><span class="section"><a href="functional/adapters/limits.html">Limits</a></span></dt> |
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| <dt><span class="section"><a href="functional/generation.html">Generation</a></span></dt> |
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| <dt><span class="section"><a href="functional/generation/functions.html">Functions</a></span></dt> |
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| <p> |
| Components to call functions and function objects and to make Fusion code callable |
| through a function object interface. |
| </p> |
| <a name="fusion.functional.header"></a><h4> |
| <a name="id1071607"></a> |
| <a class="link" href="functional.html#fusion.functional.header">Header</a> |
| </h4> |
| <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">fusion</span><span class="special">/</span><span class="identifier">functional</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| </pre> |
| <a name="fusion.functional.fused_and_unfused_forms"></a><h4> |
| <a name="id1071662"></a> |
| <a class="link" href="functional.html#fusion.functional.fused_and_unfused_forms">Fused and unfused |
| forms</a> |
| </h4> |
| <p> |
| What is a function call? |
| </p> |
| <pre class="programlisting"><span class="identifier">f</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">c</span><span class="special">)</span> |
| </pre> |
| <p> |
| It is a name and a tuple written next to each other, left-to-right. |
| </p> |
| <p> |
| Although the C++ syntax does not allow to replace <code class="literal">(a,b,c)</code> |
| with some Fusion <a class="link" href="sequence.html" title="Sequence">Sequence</a>, introducing |
| yet another function provides a solution: |
| </p> |
| <pre class="programlisting"><span class="identifier">invoke</span><span class="special">(</span><span class="identifier">f</span><span class="special">,</span><span class="identifier">my_sequence</span><span class="special">)</span> |
| </pre> |
| <p> |
| Alternatively it is possible to apply a simple transformation to <code class="literal">f</code> |
| in order to achieve the same effect: |
| </p> |
| <pre class="programlisting"><span class="identifier">f</span> <span class="identifier">tuple</span> <span class="special"><=></span> f' <span class="special">(</span><span class="identifier">tuple</span><span class="special">)</span> |
| </pre> |
| <p> |
| Now, <code class="literal">f'</code> is an unary function that takes the arguments to |
| <code class="computeroutput"><span class="identifier">f</span></code> as a tuple; <code class="literal">f'</code> |
| is the <span class="emphasis"><em>fused</em></span> form of <code class="computeroutput"><span class="identifier">f</span></code>. |
| Reading the above equivalence right-to-left to get the inverse transformation, |
| <code class="computeroutput"><span class="identifier">f</span></code> is the <span class="emphasis"><em>unfused</em></span> |
| form of <code class="literal">f'</code>. |
| </p> |
| <a name="fusion.functional.calling_functions_and_function_objects"></a><h4> |
| <a name="id1071847"></a> |
| <a class="link" href="functional.html#fusion.functional.calling_functions_and_function_objects">Calling |
| functions and function objects</a> |
| </h4> |
| <p> |
| Having generic C++ code call back arbitrary functions provided by the client |
| used to be a heavily repetitive task, as different functions can differ in |
| arity, invocation syntax and other properties that might be part of the type. |
| Transporting arguments as Fusion sequences and factoring out the invocation |
| makes Fusion algorithms applicable to function arguments and also reduces the |
| problem to one invocation syntax and a fixed arity (instead of an arbitrary |
| number of arbitrary arguments times several syntactic variants times additional |
| properties). |
| </p> |
| <p> |
| Transforming an unfused function into its fused counterpart allows n-ary calls |
| from an algorithm that invokes an unary <a class="link" href="functional/concepts/poly.html" title="Polymorphic Function Object">Polymorphic |
| Function Object</a> with <a class="link" href="sequence.html" title="Sequence">Sequence</a> |
| arguments. |
| </p> |
| <p> |
| The library provides several function templates to invoke different kinds of |
| functions and adapters to transform them into fused form, respectively. Every |
| variant has a corresponding generator function template that returns an adapter |
| instance for the given argument. |
| </p> |
| <p> |
| Constructors can be called applying <a href="http://www.boost.org/libs/functional/factory/doc/html/index.html" target="_top">Boost.Functional/Factory</a>. |
| </p> |
| <a name="fusion.functional.making_fusion_code_callable_through_a_function_object_interface"></a><h4> |
| <a name="id1071891"></a> |
| <a class="link" href="functional.html#fusion.functional.making_fusion_code_callable_through_a_function_object_interface">Making |
| Fusion code callable through a function object interface</a> |
| </h4> |
| <p> |
| Transforming a fused function into its unfused counterpart allows to create |
| function objects to accept arbitrary calls. In other words, an unary function |
| object can be implemented instead of (maybe heavily overloaded) function templates |
| or function call operators. |
| </p> |
| <p> |
| The library provides both a strictly typed and a generic variant for this transformation. |
| The latter should be used in combination with <a href="http://www.boost.org/libs/functional/forward/doc/html/index.html" target="_top">Boost.Functional/Forward</a> |
| to attack <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2002/n1385.htm" target="_top">The |
| Forwarding Problem</a>. |
| </p> |
| <p> |
| Both variants have a corresponding generator function template that returns |
| an adapter instance for the given argument. |
| </p> |
| </div> |
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| 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>) |
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