The following new types are introduced, in addition to the types defined in the Associative Container requirements.
||A type that is a model of Hash Function. X::hasher 's argument type must be X::key_type.|
||A Binary Predicate whose argument type is X::key_type . An object of type key_equal returns true if its arguments are the same key, and false otherwise. X::key_equal must be an equivalence relation.|