std::has_facet (3) - Linux Manuals

std::has_facet: std::has_facet

NAME

std::has_facet - std::has_facet

Synopsis

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

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

// Run this code

  #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