View source for cpp/locale/ctype byname

{{cpp/title|ctype_byname}}
{{cpp/locale/navbar}}
{{dcl begin}}
{{dcl header|locale}}
{{dcl|1=
template< class CharT >
class ctype_byname : public std::ctype<CharT>;
}}
{{dcl end}}

{{tt|std::ctype_byname}} is a {{lc|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:
{{dsc begin}}
{{dsc header|locale}}
{{dsc|{{c/core|std::ctype_byname<char>}}|provides narrow character classification. This specialization uses table lookup for character classification}}
{{dsc|{{c/core|std::ctype_byname<wchar_t>}}|provides wide character classification}}
{{dsc end}}

===Member types===
{{dsc begin}}
{{dsc hitem|Member type|Definition}}
{{dsc|{{tt|mask}}|{{c/core|typename std::ctype<CharT>::mask}}}}
{{dsc end}}

===Member functions===
{{dsc begin}}
{{dsc inc|cpp/locale/byname/dsc constructor|ctype_byname}}
{{dsc inc|cpp/locale/byname/dsc destructor|ctype_byname}}
{{dsc end}}

{{include|cpp/locale/byname/constructor|ctype_byname}}
{{include|cpp/locale/byname/destructor|ctype_byname}}

{{cpp/locale/ctype/inherit}}
{{cpp/locale/ctype_base/inherit}}

===Notes===
The explicit specialization {{ltt|cpp/locale/ctype byname char|std::ctype_byname<char>}} was listed as a separate entry in the header file {{header|locale}} until C++11. it was removed as {{lwg|1298}}, but it remains a required specialization, just like {{c/core|std::ctype_byname<wchar_t>}}.

===Example===
{{example
| 
|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===
{{dr list begin}}
{{dr list item|wg=lwg|dr=16|std=C++98|before=the definition of the explicit specialization {{c/core|std::ctype_byname<char>}}<br>misspecified the name and parameter list of {{tt|do_narrow}}|after=corrected}}
{{dr list item|wg=lwg|dr=616|std=C++98|before=the {{c/core|typename}} disambiguator was missing in the definition of {{tt|mask}}|after=added}}
{{dr list end}}

===See also===
{{dsc begin}}
{{dsc inc|cpp/locale/dsc ctype}}
{{dsc inc|cpp/locale/dsc ctype_char}}
{{dsc end}}

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