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Merged revisions 52740,52742,52963,53164,53320-53321,53323-53324,53326,53507,53509,53710 via svnmerge from https://svn.boost.org/svn/boost/website/public_html/beta ........ r52740 | danieljames | 2009-05-02 18:25:29 +0100 (Sat, 02 May 2009) | 1 line Merge from live, up to 52379. ........ r52742 | danieljames | 2009-05-02 18:33:49 +0100 (Sat, 02 May 2009) | 1 line Release 1.39 ........ r52963 | joaquin | 2009-05-13 11:42:54 +0100 (Wed, 13 May 2009) | 1 line merged [52962] from live website ........ r53164 | danieljames | 2009-05-21 22:33:28 +0100 (Thu, 21 May 2009) | 1 line Make the check for '<body' case insensitive when processing the doucmentation. ........ r53320 | danieljames | 2009-05-27 20:23:01 +0100 (Wed, 27 May 2009) | 1 line Add link to 'Die Boost C++ Bibliotheken' to bibliography. ........ r53321 | danieljames | 2009-05-27 20:23:10 +0100 (Wed, 27 May 2009) | 1 line Correct mime type for csshover.htc ........ r53323 | danieljames | 2009-05-27 20:50:45 +0100 (Wed, 27 May 2009) | 2 lines Upgrade to css hover 3 and only use it for IE 7 as it causes IE 6 to crash and isn't needed on IE 8. ........ r53324 | danieljames | 2009-05-27 20:51:26 +0100 (Wed, 27 May 2009) | 1 line Try to prevent wide content on sidebar from messing up layout on IE. ........ r53326 | danieljames | 2009-05-27 21:46:51 +0100 (Wed, 27 May 2009) | 1 line Try to deal with content overflowing in the directory element in IE6. ........ r53507 | danieljames | 2009-05-31 18:53:02 +0100 (Sun, 31 May 2009) | 1 line Missing redirect for writingdoc. ........ r53509 | danieljames | 2009-05-31 19:05:53 +0100 (Sun, 31 May 2009) | 1 line Link to the wiki on the front page. ........ r53710 | danieljames | 2009-06-07 11:32:33 +0100 (Sun, 07 Jun 2009) | 1 line Add a hook for pre-processing the extracted file from the zipfile. ........ [SVN r53714]
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5.3 KiB
HTML
123 lines
5.3 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
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"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
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<head>
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<title>Boost Library Reuse</title>
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<meta http-equiv="Content-Type" content="text/html; charset=us-ascii" />
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<link rel="icon" href="/favicon.ico" type="image/ico" />
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<link rel="stylesheet" type="text/css" href=
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"/style/section-development.css" />
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<!--[if IE 7]> <style type="text/css"> body { behavior: url(/style/csshover3.htc); } </style> <![endif]-->
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</head><!--
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Note: Editing website content is documented at:
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http://www.boost.org/development/website_updating.html
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-->
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<body>
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<div id="heading">
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<!--#include virtual="/common/heading.html" -->
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</div>
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<div id="body">
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<div id="body-inner">
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<div id="content">
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<div class="section" id="intro">
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<div class="section-0">
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<div class="section-title">
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<h1>Boost Library reuse: cost versus benefit trade-offs</h1>
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</div>
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<div class="section-body">
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<p>A Boost library <strong>should not</strong> use libraries
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other than Boost or the C++ Standard Library.</p>
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<p>A Boost library <strong>should</strong> use other Boost
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Libraries or the C++ Standard Library, but only when the
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benefits outweigh the costs.</p>
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<p>The benefits of using components from other libraries may
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include clearer, more understandable code, reduced development
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and maintenance costs, and the assurance which comes from
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reusing well-known and trusted building blocks.</p>
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<p>The costs may include undesirable coupling between
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components, and added compilation and runtime costs. If the
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interface to the additional component is complex, using it may
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make code less readable, and thus actually increase development
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and maintenance costs.</p>
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<p>Negative effects of coupling become obvious when one library
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uses a second library which uses a third, and so on. The worst
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form of coupling requires the user understand each of the
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coupled libraries. Coupling may also reduce the portability of
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a library - even in case when all used libraries are
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self-sufficient (see example of questionable usage of
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<iostream> library below).</p>
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<p><strong>Example where another boost component should
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certainly be used:</strong> boost::noncopyable (in <a href=
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"/doc/libs/release/boost/utility.hpp">boost/utility.hpp</a>)
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has considerable benefits; it simplifies code, improves
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readability, and signals intent. Costs are low as coupling is
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limited; noncopyable itself uses no other classes and its
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header includes only the lightweight headers
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<boost/config.hpp> and <cstddef>. There are no
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runtime costs at all. With costs so low and benefits so high,
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other boost libraries should use boost::noncopyable when the
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need arises except in exceptional circumstances.</p>
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<p><strong>Example where a standard library component might
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possibly be used:</strong> Providing diagnostic output as a
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debugging aid can be a nice feature for a library. Yet using
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Standard Library <iostream> can involves a lot of
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additional cost, particularly if <iostream> is unlikely
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to be use elsewhere in the application. In certain GUI or
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embedded applications, coupling to <iostream> would be a
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disqualification. Consider redesign of the boost library in
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question so that the user supplies the diagnostic output
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mechanism.</p>
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<p><strong>Example where another boost component should not be
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used:</strong> The boost dir_it library has considerable
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coupling and runtime costs, not to mention portability issues
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for unsupported operating systems. While completely appropriate
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when directory iteration is required, it would not be
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reasonable for another boost library to use dir_it just to
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check that a file is available before opening. C++ Standard
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Library file open functionality does this at lower cost. Don't
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use dir_it just for the sake of using a boost library.</p>
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</div>
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</div>
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</div>
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</div>
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<div id="sidebar">
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<!--#include virtual="/common/sidebar-common.html" -->
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<!--#include virtual="/common/sidebar-development.html" -->
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</div>
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<div class="clear"></div>
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</div>
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</div>
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<div id="footer">
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<div id="footer-left">
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<div id="revised">
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<p>Revised $Date: 2007-10-22 22:55:52 +0100 (Mon, 22 Oct 2007) $</p>
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</div>
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<div id="copyright">
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<p>Copyright Beman Dawes 2000.</p>
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</div><!--#include virtual="/common/footer-license.html" -->
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</div>
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<div id="footer-right">
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<!--#include virtual="/common/footer-banners.html" -->
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</div>
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<div class="clear"></div>
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</div>
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</body>
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</html>
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