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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd">
<!-- Copyright (c) 2002-2006 Pavol Droba.
Subject to the Boost Software License, Version 1.0.
(See accompanying file LICENSE-1.0 or http://www.boost.org/LICENSE-1.0)
-->
<section id="string_algo.rationale" last-revision="$Date: 2006/08/16 07:10:48 $">
<title>Rationale</title>
<using-namespace name="boost"/>
<using-namespace name="boost::algorithm"/>
<section it="string_algo.locale">
<title>Locales</title>
<para>
Locales have a very close relation to string processing. They contain information about
the character sets and are used, for example, to change the case of characters and
to classify the characters.
</para>
<para>
C++ allows to work with multiple different instances of locales at once. If an algorithm
manipulates some data in a way that requires the usage of locales, there must be a way
to specify them. However, one instance of locales is sufficient for most of the applications,
and for a user it could be very tedious to specify which locales to use at every place
where it is needed.
</para>
<para>
Fortunately, the C++ standard allows to specify the <emphasis>global</emphasis> locales (using static member
function <code>std:locale::global()</code>). When instantiating an
<code>std::locale</code> class without explicit information, the instance will
be initialized with the <emphasis>global</emphasis> locale. This implies, that if an algorithm needs a locale,
it should have an <code>std::locale</code> parameter defaulting to <code>std::locale()</code>.
If a user needs to specify locales explicitly, she can do so. Otherwise the <emphasis>global</emphasis>
locales are used.
</para>
</section>
<section id="string_algo.regex">
<title>Regular Expressions</title>
<para>
Regular expressions are an essential part of text processing. For this reason, the library
also provides regex variants of some algorithms. The library does not attempt to replace
<libraryname>Boost.Regex</libraryname>; it merely wraps its functionality in a new interface.
As a part of this library, regex algorithms integrate smoothly with other components, which
brings additional value.
</para>
</section>
</section>
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