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std::has_facet

Defined in header <locale> 
template< class Facet >
bool has_facet( const locale& loc );

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.

Exceptions

(none) (until C++11)
noexcept specification:
noexcept
 (since C++11)

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

See also

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

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