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53 lines
2.6 KiB
XML
53 lines
2.6 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
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"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd">
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<!-- Copyright (c) 2002-2006 Pavol Droba.
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Subject to the Boost Software License, Version 1.0.
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(See accompanying file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)
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-->
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<section id="string_algo.rationale" last-revision="$Date$">
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<title>Rationale</title>
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<using-namespace name="boost"/>
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<using-namespace name="boost::algorithm"/>
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<section it="string_algo.locale">
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<title>Locales</title>
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<para>
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Locales have a very close relation to string processing. They contain information about
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the character sets and are used, for example, to change the case of characters and
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to classify the characters.
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</para>
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<para>
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C++ allows to work with multiple different instances of locales at once. If an algorithm
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manipulates some data in a way that requires the usage of locales, there must be a way
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to specify them. However, one instance of locales is sufficient for most of the applications,
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and for a user it could be very tedious to specify which locales to use at every place
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where it is needed.
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</para>
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<para>
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Fortunately, the C++ standard allows to specify the <emphasis>global</emphasis> locales (using static member
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function <code>std:locale::global()</code>). When instantiating an
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<code>std::locale</code> class without explicit information, the instance will
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be initialized with the <emphasis>global</emphasis> locale. This implies, that if an algorithm needs a locale,
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it should have an <code>std::locale</code> parameter defaulting to <code>std::locale()</code>.
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If a user needs to specify locales explicitly, she can do so. Otherwise the <emphasis>global</emphasis>
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locales are used.
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</para>
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</section>
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<section id="string_algo.regex">
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<title>Regular Expressions</title>
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<para>
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Regular expressions are an essential part of text processing. For this reason, the library
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also provides regex variants of some algorithms. The library does not attempt to replace
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<libraryname>Boost.Regex</libraryname>; it merely wraps its functionality in a new interface.
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As a part of this library, regex algorithms integrate smoothly with other components, which
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brings additional value.
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</para>
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</section>
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</section>
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