An Inserter for Phone Numbers

Apache C++ Standard Library User's Guide

26.4 An Inserter for Phone Numbers

Now let's take a look at the implementation of the inserter for our phone number class:

std::ostream& operator<< (std::ostream& os, const PhoneNumber& pn){
  std::locale loc = os.getloc ();                           // 1
  const phone_put& ppFacet 
                     = std::use_facet<phone_put> (loc);     // 2
  os << ppFacet.put(pn._cntryName,
                    pn._areaCode, pn._extension);           // 3
  return (os);
}

`//1`	The inserter function uses the output stream's locale object (obtained via `getloc()`),
`//2`	uses the locale's phone number facet object,
`//3`	and calls the facet object's formatting service `put()`.