std::has_facet

Defined in header `<locale>`
template< class Facet > bool has_facet( const locale& loc ) throw();		(until C++11)
template< class Facet > bool has_facet( const locale& loc ) noexcept;		(since C++11)

Checks if the locale loc implements the facet Facet.

Parameters

loc

the locale object to query

Return value

Returns true if the facet Facet was installed in the locale loc, false otherwise.

Example

#include <iostream>
#include <locale>
 
// minimal custom facet
struct myfacet : public std::locale::facet {
    static std::locale::id id;
};
 
std::locale::id myfacet::id;
 
int main()
{
    // loc is a "C" locale with myfacet added
    std::locale loc(std::locale::classic(), new myfacet);
    std::cout << std::boolalpha
              << "Can loc classify chars? "
              << std::has_facet<std::ctype<char>>(loc) << '\n'
              << "Can loc classify char32_t? "
              << std::has_facet<std::ctype<char32_t>>(loc) << '\n'
              << "Does loc implement myfacet? "
              << std::has_facet<myfacet>(loc) << '\n';
}

Output:

Can loc classify chars? true
Can loc classify char32_t? false
Does loc implement myfacet? true

locale	set of polymorphic facets that encapsulate cultural differences (class)
use_facet	obtains a facet from a locale (function template)

std::has_facet

Parameters

Return value

Example

See also