The <locale>
header declares class and function templates for
internationalization and localization. It supports conversion between
narrow and wide character sets, character classification and collation,
formatting and parsing numbers, currency, dates and times, and
retrieving messages. For example, every I/O stream has a locale, which
it uses to parse formatted input or to format output.
A locale is an embodiment of a set of cultural conventions, including information about the native character set, how dates are formatted, which symbol to use for currency, and so on. Each set of related attributes is called a facet, which are grouped into categories.
The categories are fixed and defined by the standard (see Table 13-20, under locale::category
, for a complete list), and
each category has several predefined facets. For example, one of the
facets in the time category is time_get<charT
, InputIter>
, which specifies rules for
parsing a time string. You can define additional facets; see the
description of the locale::facet
class in this section for details.
Many of the facets come in two flavors: plain and named. The plain
versions implement default behavior, and the named versions implement
the behavior for a named locale. See the locale
class later in this section for a
discussion of locale names.
When a program starts, the global locale is initialized to the
"C
" locale, and the standard I/O
streams use this locale for character conversions and formatting. A
program can change the locale at any time; see the locale
class in this section for
details.
The C++ <locale>
header
provides more functionality than the C <clocale>
, <cctype>
, and <cwchar>
headers, especially the ability
to extend a locale with your own facets. On the other hand, facets and
the locale class template are more complicated than the C functions. For
simple character classification in a single locale, you are probably
better off using the C functions. If a program must work with multiple
locales simultaneously, use the C++ locale
template.