std::ctype_byname

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< cpp‎ | locale
 
C++
 
Localization library
 
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

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

Protected member functions

[virtual]
 converts a character or characters to uppercase
(virtual protected member function of std::ctype<CharT>)
[virtual]
 converts a character or characters to lowercase
(virtual protected member function of std::ctype<CharT>)
[virtual]
 converts a character or characters from char to CharT
(virtual protected member function of std::ctype<CharT>)
[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
[virtual]
 classifies a character or a character sequence
(virtual protected member function of std::ctype<CharT>)
[virtual]
 locates the first character in a sequence that conforms to given classification
(virtual protected member function of std::ctype<CharT>)
[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

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