C++ In a Nutshell

Name

has_facet function template — Test for existence of a facet in a locale

Synopsis

template <typename Facet>
bool has_facet(const locale& loc) throw(  );

The has_facet function determines whether the locale loc supports the facet Facet. It returns true if the facet is supported or false if it is not. Call has_facet to determine whether a locale supports a user-defined facet. (Every locale must support the standard facets that are described in this section.) Example 13-24 shows how has_facet is used.

Example

Example 13-24. Testing whether a locale supports a facet

// The units facet is defined under the locale::facet class (later in this
// section).
   
using std::locale;
if (std::has_facet<units>(locale(  )) {
  // Get a reference to the units facet of the locale.
  const units& u = std::use_facet<units>(locale(  ));
  // Construct a value of 42 cm.
  units::value_t len = u.make(42, units::cm);
  // Print the length (42 cm) in the locale's preferred units.
  u.length_put(std::cout, len);
}

See Also

locale class, use_facet function template