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https://svn.boost.org/svn/boost/trunk ........ r42067 | johnmaddock | 2007-12-15 04:32:18 -0800 (Sat, 15 Dec 2007) | 1 line MSVC warning suppression. ........ r42069 | bemandawes | 2007-12-15 06:26:16 -0800 (Sat, 15 Dec 2007) | 1 line Correct misspelling of library name ........ r42074 | johnmaddock | 2007-12-15 09:10:03 -0800 (Sat, 15 Dec 2007) | 1 line Fix error messages so they work with Boost.Format. ........ r42076 | johnmaddock | 2007-12-15 09:36:31 -0800 (Sat, 15 Dec 2007) | 1 line Trivial patches to silence MSVC warnings. ........ r42078 | johnmaddock | 2007-12-15 10:29:29 -0800 (Sat, 15 Dec 2007) | 1 line Disable long double tests if there's no long double support. ........ r42080 | johnmaddock | 2007-12-15 10:49:13 -0800 (Sat, 15 Dec 2007) | 1 line Yet another MSVC warning suppression. ........ r42082 | bgubenko | 2007-12-15 10:53:01 -0800 (Sat, 15 Dec 2007) | 1 line mark up Boost.Test tests for Linux ia64 gcc; make Boost.Interprocess unsupported on Linux ia64 gcc and PA-RISC ........ r42086 | anthonyw | 2007-12-15 14:34:30 -0800 (Sat, 15 Dec 2007) | 1 line added timed_wait overloads that take a duration ........ r42087 | anthonyw | 2007-12-15 14:36:43 -0800 (Sat, 15 Dec 2007) | 1 line explicit move functions for threads, with a test ........ r42105 | andreas_huber69 | 2007-12-16 06:58:24 -0800 (Sun, 16 Dec 2007) | 1 line Removed markup for now passing Sandia tests. ........ r42112 | bemandawes | 2007-12-16 14:39:32 -0800 (Sun, 16 Dec 2007) | 1 line Add intel-win-10.0 as required ........ r42116 | djowel | 2007-12-17 01:27:42 -0800 (Mon, 17 Dec 2007) | 1 line fixed documentation bug ........ r42117 | anthonyw | 2007-12-17 03:24:13 -0800 (Mon, 17 Dec 2007) | 1 line Updated move function test to be fair to Borland ........ r42118 | anthonyw | 2007-12-17 04:52:50 -0800 (Mon, 17 Dec 2007) | 1 line boost::move support for locks ........ r42119 | chris_kohlhoff | 2007-12-17 05:04:30 -0800 (Mon, 17 Dec 2007) | 2 lines Fixes for older HP-UX. ........ r42120 | chris_kohlhoff | 2007-12-17 05:08:10 -0800 (Mon, 17 Dec 2007) | 2 lines Bump version number. ........ r42121 | chris_kohlhoff | 2007-12-17 05:17:46 -0800 (Mon, 17 Dec 2007) | 2 lines Documentation fixes. ........ r42127 | bgubenko | 2007-12-17 10:06:11 -0800 (Mon, 17 Dec 2007) | 1 line markup test library test prg_exec_fail2 for PA-RISC ........ r42138 | johnmaddock | 2007-12-18 08:37:23 -0800 (Tue, 18 Dec 2007) | 1 line Fixes #1525. ........ r42141 | marshall | 2007-12-18 10:33:55 -0800 (Tue, 18 Dec 2007) | 1 line Patches to fixe #1423 and #1473 ........ r42145 | fmhess | 2007-12-18 12:14:01 -0800 (Tue, 18 Dec 2007) | 4 lines Prevented "classname"/"methodname"/etc. elements inside "type" elements inside "static-constant" elements from getting dropped. ........ r42164 | djowel | 2007-12-19 02:33:14 -0800 (Wed, 19 Dec 2007) | 1 line bug fix for end_impl. ........ r42165 | djowel | 2007-12-19 02:33:39 -0800 (Wed, 19 Dec 2007) | 1 line bug fix for end_impl. (test) ........ r42166 | anthonyw | 2007-12-19 02:39:45 -0800 (Wed, 19 Dec 2007) | 1 line Updated thread ID, and added tests ........ r42167 | djowel | 2007-12-19 02:42:04 -0800 (Wed, 19 Dec 2007) | 1 line tweakbug fix for end_impl (tweak). ........ r42168 | anthonyw | 2007-12-19 02:45:01 -0800 (Wed, 19 Dec 2007) | 1 line Implement hardware_concurrency for pthread ........ r42169 | johnmaddock | 2007-12-19 08:41:54 -0800 (Wed, 19 Dec 2007) | 1 line Fix graph title. ........ [SVN r42185]
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
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<a name="fusion.algorithm"></a><a href="algorithm.html" title="Algorithm">Algorithm</a></h2></div></div></div>
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<dt><span class="section"><a href="algorithm/iteration.html">Iteration</a></span></dt>
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<a name="fusion.algorithm.lazy_evaluation"></a><h3>
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<a href="algorithm.html#fusion.algorithm.lazy_evaluation">Lazy Evaluation</a>
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Unlike <a href="http://www.boost.org/libs/mpl/index.html" target="_top">MPL</a>, Fusion
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algorithms are lazy and non sequence-type preserving. What does that mean?
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It means that when you operate on a sequence through a Fusion algorithm that
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returns a sequence, the sequence returned may not be of the same class as the
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original. This is by design. Runtime efficiency is given a high priority. Like
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<a href="http://en.wikipedia.org/wiki/Standard_Template_Library" target="_top">STL</a>,
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fusion algorithms are functional in nature such that algorithms are non mutating
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(no side effects). However, due to the high cost of returning full sequences
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such as vectors and lists, <span class="emphasis"><em>Views</em></span> are returned from Fusion
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algorithms instead. For example, the <a href="algorithm/transformation/functions/transform.html" title="transform"><tt class="computeroutput"><span class="identifier">transform</span></tt></a> algorithm does not actually
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return a transformed version of the original sequence. <a href="algorithm/transformation/functions/transform.html" title="transform"><tt class="computeroutput"><span class="identifier">transform</span></tt></a> returns a <a href="view/transform_view.html" title="transform_view"><tt class="computeroutput"><span class="identifier">transform_view</span></tt></a>. This view holds a
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reference to the original sequence plus the transform function. Iteration over
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the <a href="view/transform_view.html" title="transform_view"><tt class="computeroutput"><span class="identifier">transform_view</span></tt></a>
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will apply the transform function over the sequence elements on demand. This
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<a href="algorithm.html#fusion.algorithm.sequence_extension">Sequence Extension</a>
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The <span class="emphasis"><em>lazy</em></span> evaluation scheme where <a href="algorithm.html" title="Algorithm">Algorithms</a>
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return <a href="view.html" title="View">Views</a> also allows operations such
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as <a href="algorithm/transformation/functions/push_back.html" title="push_back"><tt class="computeroutput"><span class="identifier">push_back</span></tt></a> to be totally generic. In
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Fusion, <a href="algorithm/transformation/functions/push_back.html" title="push_back"><tt class="computeroutput"><span class="identifier">push_back</span></tt></a> is actually a generic algorithm
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that works on all sequences. Given an input sequence <tt class="computeroutput"><span class="identifier">s</span></tt>
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and a value <tt class="computeroutput"><span class="identifier">x</span></tt>, Fusion's <a href="algorithm/transformation/functions/push_back.html" title="push_back"><tt class="computeroutput"><span class="identifier">push_back</span></tt></a> algorithm simply returns
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a <a href="view/joint_view.html" title="joint_view"><tt class="computeroutput"><span class="identifier">joint_view</span></tt></a>:
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a view that holds a reference to the original sequence <tt class="computeroutput"><span class="identifier">s</span></tt>
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and the value <tt class="computeroutput"><span class="identifier">x</span></tt>. Functions
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that were once sequence specific and need to be implemented N times over N
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different sequences are now implemented only once. That is to say that Fusion
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sequences are cheaply extensible. However, an important caveat is that the
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<a href="container/conversion/functions.html" title="Functions">Conversion</a> functions
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are provided. You may use one of the <a href="container/conversion/functions.html" title="Functions">Conversion</a>
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functions to convert back to the original sequence type.
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</p>
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<a name="fusion.algorithm.header"></a><h3>
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<a name="id578165"></a>
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<a href="algorithm.html#fusion.algorithm.header">Header</a>
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</h3>
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<pre class="programlisting">
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<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">algorithm</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
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<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">include</span><span class="special">/</span><span class="identifier">algorithm</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
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</pre>
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<td align="right"><div class="copyright-footer">Copyright © 2001-2007 Joel de Guzman, Dan Marsden, Tobias
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Schwinger<p>
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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