std::ctype_byname

 

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Localizations library

Locales and facets
Locales
has_facet use_facet	locale
Facet category base classes
ctype_base codecvt_base messages_base	time_base money_base
ctype facets
ctype ctype_byname ctype<char>	codecvt codecvt_byname
numeric facets
num_get num_put	numpunct numpunct_byname
collate facets
collate	collate_byname
time facets
time_get time_get_byname	time_put time_put_byname
monetary facets
money_get money_put	moneypunct moneypunct_byname
messages facets
messages	messages_byname
Character classification and conversion
Character classification
isspace isblank (C++11) iscntrl isupper islower isalpha	isdigit ispunct isxdigit isalnum isprint isgraph
Conversions
toupper tolower	wstring_convert (C++11/17*) wbuffer_convert (C++11/17*)
Code conversion facets
codecvt_utf8 (C++11/17*) codecvt_utf16 (C++11/17*)	codecvt_utf8_utf16 (C++11/17*) codecvt_mode (C++11/17*)
C locale
LC_ALLLC_COLLATELC_CTYPELC_MONETARYLC_NUMERICLC_TIME	setlocale localeconv lconv

 

Defined in header <locale>
template< class CharT > class ctype_byname : public std::ctype<CharT>;

std::ctype_byname is a std::ctype facet which encapsulates character classification rules of the locale specified at its construction.

Specializations

The standard library is guaranteed to provide the following specializations:

Defined in header <locale>
std::ctype_byname<char>	provides narrow character classification. This specialization uses table lookup for character classification
std::ctype_byname<wchar_t>	provides wide character classification

Member types

Member type	Definition
mask	typename std::ctype<CharT>::mask

Member functions

(constructor)	constructs a new ctype_byname facet (public member function)
(destructor)	destroys a ctype_byname facet (protected member function)

std::ctype_byname::ctype_byname

explicit ctype_byname( const char* name, std::size_t refs = 0 );
explicit ctype_byname( const std::string& name, std::size_t refs = 0 );		(since C++11)

Constructs a new std::ctype_byname facet for a locale with name.

refs is used for resource management: if refs == 0, the implementation destroys the facet, when the last std::locale object holding it is destroyed. Otherwise, the object is not destroyed.

Parameters

name	-	the name of the locale
refs	-	the number of references that link to the facet

std::ctype_byname::~ctype_byname

protected: ~ctype_byname();

Destroys the facet.

Inherited from std::ctype<CharT>

Member types

Member type	Definition
char_type	CharT

Member objects

Member name	Type
static std::locale::id id [static]	id of the locale (public static member constant)
if CharT is char, the following member of std::ctype<char> is inherited
static const std::size_t table_size [static]	size of the classification table, at least 256 (public static member constant)

Member functions

is	invokes do_is (public member function of std::ctype<CharT>)
scan_is	invokes do_scan_is (public member function of std::ctype<CharT>)
scan_not	invokes do_scan_not (public member function of std::ctype<CharT>)
toupper	invokes do_toupper (public member function of std::ctype<CharT>)
tolower	invokes do_tolower (public member function of std::ctype<CharT>)
widen	invokes do_widen (public member function of std::ctype<CharT>)
narrow	invokes do_narrow (public member function of std::ctype<CharT>)
if CharT is char, the following members of std::ctype<char> are inherited
table	obtains the character classification table (public member function of std::ctype<char>)
classic_table [static]	obtains the "C" locale character classification table (public static member function of std::ctype<char>)

Protected member functions

do_toupper [virtual]	converts a character or characters to uppercase (virtual protected member function of std::ctype<CharT>)
do_tolower [virtual]	converts a character or characters to lowercase (virtual protected member function of std::ctype<CharT>)
do_widen [virtual]	converts a character or characters from char to CharT (virtual protected member function of std::ctype<CharT>)
do_narrow [virtual]	converts a character or characters from CharT to char (virtual protected member function of std::ctype<CharT>)
if CharT is char, the following members of std::ctype are NOT inherited
do_is [virtual]	classifies a character or a character sequence (virtual protected member function of std::ctype<CharT>)
do_scan_is [virtual]	locates the first character in a sequence that conforms to given classification (virtual protected member function of std::ctype<CharT>)
do_scan_not [virtual]	locates the first character in a sequence that fails given classification (virtual protected member function of std::ctype<CharT>)

Inherited from std::ctype_base

Member types

Type	Definition
mask	unspecified bitmask type (enumeration, integer type, or bitset)

Member constants

space [static]	the value of mask identifying whitespace character classification (public static member constant)
print [static]	the value of mask identifying printable character classification (public static member constant)
cntrl [static]	the value of mask identifying control character classification (public static member constant)
upper [static]	the value of mask identifying uppercase character classification (public static member constant)
lower [static]	the value of mask identifying lowercase character classification (public static member constant)
alpha [static]	the value of mask identifying alphabetic character classification (public static member constant)
digit [static]	the value of mask identifying digit character classification (public static member constant)
punct [static]	the value of mask identifying punctuation character classification (public static member constant)
xdigit [static]	the value of mask identifying hexadecimal digit character classification (public static member constant)
blank [static] (C++11)	the value of mask identifying blank character classification (public static member constant)
alnum [static]	alpha | digit (public static member constant)
graph [static]	alnum | punct (public static member constant)

Notes

The explicit specialization std::ctype_byname<char> was listed as a separate entry in the header file <locale> until C++11. it was removed as LWG issue 1298, but it remains a required specialization, just like std::ctype_byname<wchar_t>.

Example

Run this code

#include <iostream>
#include <locale>
 
int main()
{
    wchar_t c = L'\u00de'; // capital letter thorn
 
    std::locale loc("C");
 
    std::cout << "isupper('Þ', C locale) returned "
              << std::boolalpha << std::isupper(c, loc) << '\n';
 
    loc = std::locale(loc, new std::ctype_byname<wchar_t>("en_US.utf8"));
 
    std::cout << "isupper('Þ', C locale with Unicode ctype) returned "
              << std::boolalpha << std::isupper(c, loc) << '\n';
}

Output:

isupper('Þ', C locale) returned false
isupper('Þ', C locale with Unicode ctype) returned true

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 16	C++98	the definition of the explicit specialization std::ctype_byname<char> misspecified the name and parameter list of do_narrow	corrected
LWG 616	C++98	the typename disambiguator was missing in the definition of mask	added

See also

ctype	defines character classification tables (class template)
ctype<char>	specialization of std::ctype for type char (class template specialization)