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https://svn.boost.org/svn/boost/trunk ........ r40862 | dave | 2007-11-06 15:39:09 -0800 (Tue, 06 Nov 2007) | 2 lines Added missing copyright/license ........ r40863 | djowel | 2007-11-06 18:12:28 -0800 (Tue, 06 Nov 2007) | 1 line added copyright and license info for each page. ........ r40864 | aaron_windsor | 2007-11-06 18:30:38 -0800 (Tue, 06 Nov 2007) | 1 line Shortening file name of a graph test to < 32 characters ........ r40865 | djowel | 2007-11-06 18:34:18 -0800 (Tue, 06 Nov 2007) | 1 line added license info in copyright notice at the footer ........ r40866 | djowel | 2007-11-06 19:06:23 -0800 (Tue, 06 Nov 2007) | 1 line added license info in copyright notice at the footer ........ r40867 | djowel | 2007-11-06 19:23:31 -0800 (Tue, 06 Nov 2007) | 1 line added license info in copyright notice at the footer ........ r40868 | djowel | 2007-11-06 19:25:59 -0800 (Tue, 06 Nov 2007) | 1 line added copyright and license info for each page. ........ r40869 | djowel | 2007-11-06 19:27:38 -0800 (Tue, 06 Nov 2007) | 1 line added license info in copyright notice at the footer ........ r40870 | djowel | 2007-11-06 19:30:01 -0800 (Tue, 06 Nov 2007) | 1 line added copyright and license info for each page. ........ r40871 | djowel | 2007-11-06 19:35:49 -0800 (Tue, 06 Nov 2007) | 1 line added copyright and license info for each page. ........ r40872 | djowel | 2007-11-06 19:37:51 -0800 (Tue, 06 Nov 2007) | 1 line added copyright and license info for each page. ........ r40873 | djowel | 2007-11-06 19:46:23 -0800 (Tue, 06 Nov 2007) | 1 line added copyright and license info for each page. ........ r40874 | chris_kohlhoff | 2007-11-06 22:49:36 -0800 (Tue, 06 Nov 2007) | 2 lines Add copyright notice. ........ r40875 | chris_kohlhoff | 2007-11-06 22:53:17 -0800 (Tue, 06 Nov 2007) | 2 lines Add myself as asio maintainer. ........ r40876 | chris_kohlhoff | 2007-11-06 23:23:53 -0800 (Tue, 06 Nov 2007) | 2 lines Add asio. ........ r40877 | joaquin | 2007-11-07 00:45:27 -0800 (Wed, 07 Nov 2007) | 1 line reapplied change at rev 40284 ........ r40878 | johnmaddock | 2007-11-07 02:07:08 -0800 (Wed, 07 Nov 2007) | 1 line Ooops, got the pp-logic wrong and disable long double support for all Unix platforms, instead of just Intel on Linux prior to version 10. ........ r40879 | johnmaddock | 2007-11-07 02:09:50 -0800 (Wed, 07 Nov 2007) | 1 line Fix calls to fpclassify so they don't trigger macro expansion when fpclassify is a macro. ........ r40880 | t_schwinger | 2007-11-07 02:14:42 -0800 (Wed, 07 Nov 2007) | 3 lines adds FunctionTypes ........ r40881 | johnmaddock | 2007-11-07 03:50:02 -0800 (Wed, 07 Nov 2007) | 1 line Change test (again) so that the range of values tested matches original test: last change started testing more extreme input values, which caused regressions on Mac OS X. ........ r40882 | johnmaddock | 2007-11-07 03:59:39 -0800 (Wed, 07 Nov 2007) | 3 lines Disabled use of long double when BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS is defined. Disabled special-double precision error rates when BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS is defined. ........ r40883 | johnmaddock | 2007-11-07 04:04:01 -0800 (Wed, 07 Nov 2007) | 1 line Oops get the name of test right! ........ r40884 | anthonyw | 2007-11-07 04:10:17 -0800 (Wed, 07 Nov 2007) | 1 line Added missing licence and copyright ........ r40885 | garcia | 2007-11-07 04:25:16 -0800 (Wed, 07 Nov 2007) | 2 lines added logging library. ........ r40886 | garcia | 2007-11-07 05:38:53 -0800 (Wed, 07 Nov 2007) | 2 lines Exception was accepted. ........ r40887 | fcacciola | 2007-11-07 06:12:15 -0800 (Wed, 07 Nov 2007) | 1 line Added explicit failures for newly discovered GCC const ref binding bug (see Ticket #1301) ........ [SVN r40891]
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114 lines
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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 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://www.boost.org/libs/mpl/index.html" target="_top">MPL</a>, and unlike
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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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<span class="emphasis"><em>lazy</em></span> evaluation scheme allows us to chain as many algorithms
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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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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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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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<a name="fusion.algorithm.header"></a><h3>
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<a name="id575155"></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"><small>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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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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