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.


loc - the locale object to query

Return value

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


#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';


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

See also

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

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