5.4 An Inserter for Phone Numbers

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

ostream& operator<<(ostream& os, const phoneNo& pn)
{ 
 locale loc = os.getloc();                                    //1
 const phone_put& ppFacet = use_facet<phone_put> (loc);       //2
 os << ppFacet.put(pn.extension, pn.areaCode, pn.countryCode);//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().