std::ctype_byname

 

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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<char> ctype_byname codecvt codecvt_byname numeric facets num_get num_put numpunct numpunct_byname collate facets collate collate_byname time facets time_get time_put time_get_byname time_put_byname

monetary facets money_get money_put moneypunct moneypunct_byname messages facets messages messages_byname Character classification and conversion Character classification isspace    iscntrl isupper islower    isalpha ispunct isdigit    isxdigit isalnum isblank (C++11) isprint isgraph Character conversions toupper    tolower String and stream conversions wstring_convert (C++11)(until C++26) wbuffer_convert (C++11)(until C++26) Unicode conversion facets codecvt_utf8 (C++11)(until C++26) codecvt_utf16 (C++11)(until C++26) codecvt_utf8_utf16 (C++11)(until C++26) codecvt_mode (C++11)(until C++26) C library locales 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 (uses table lookup for character classification)
std::ctype_byname<wchar_t>	provides wide character classification

Nested types

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> (only if CharT is not char)

Nested types

Type	Definition
char_type	CharT

Data members

Member	Description
std::locale::id id [static]	the identifier of the facet

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>)

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>)
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<char> (only if CharT is char)

Nested types

Type	Definition
char_type	char

Data members

Member	Description
std::locale::id id [static]	the identifier of the facet
const std::size_t table_size [static]	size of the classification table, at least 256

Member functions

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>)
is	classifies a character or a character sequence, using the classification table (public member function of std::ctype<char>)
scan_is	locates the first character in a sequence that conforms to given classification, using the classification table (public member function of std::ctype<char>)
scan_not	locates the first character in a sequence that fails given classification, using the classification table (public member function of std::ctype<char>)
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>)

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>)

Inherited from std::ctype_base

Nested types

Type	Definition
mask	unspecified BitmaskType 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

std::ctype_byname<char> was incorrectly declared as an explicit specialization in the synopsis of <locale>, and the declaration was removed by the resolution of 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)