has_facet()

Library:  Localization

Function

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A function template used to determine if a locale has a given facet

#include <locale>

namespace std {
  template <class Facet> 
  bool has_facet(const locale&) throw();
}

The function has_facet() returns true if the requested facet is available in the locale. Otherwise, it returns false. You specify the facet type by explicitly including the template parameter (see the example below).

//
//  hasfacet.cpp
//
 
#include <iostream>   // for cout, endl
#include <locale>     // for has_facet



// dummy facet, must derive from locale::facet
// and define a static member of type locale::id
struct my_facet: public std::locale::facet
{
    static std::locale::id id;
};

std::locale::id my_facet::id;


int main ()
{
    // see if ctype<char> is contained in the locale 
    // imbued in cout
    std::cout << std::boolalpha
      << std::has_facet<std::ctype<char> >(std::cout.getloc ())
      << std::endl;
 
    // see if my_facet is contained in the locale 
    // imbued in cout
    std::cout << std::has_facet<my_facet>(std::cout.getloc ())
       << std::endl;

    return 0;
}


Program Output:

false
false

locale, Facets, use_facet()

ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 22.1