Is there a way to query a std::locale for a list of all facets currently installed?

Question

I am familiar with the use of std::has_facet(loc) to determine whether a specific facet has been loaded into a locale.

if ( ! std::has_facet<custom_facet_t>(std::cout.getloc()) ) {
   /* load facet in to locale */
}

Is there a way to get a list of all facets currently loaded? Given the nature of locales, I am fairly certain that it would violate all types of rules... but I had to ask :) .

Answer 1

I believe (as you've surmised) that the answer is no. The locale class supports construction, assignment, name retrieval, comparison (or equality and inequality only), and function-invocation. The only (required) free functions are use_facet and has_facet, along with the is* and to* convenience interfaces.

There's simply nothing there that looks like it can support enumeration/traversal/iteration.