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<section id="string_algo.rationale" last-revision="$Date$">

<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>