c++11 - unordered_map with iterators as keys, cast iterator to long long? -

unfortunatly this:

unordered_map<list<int>::iterator, int> foo; 

does not work, compiler says: error c2338: c++ standard doesn't provide hash type.

there seems hash 64 bit integers though, save use

unordered_map<long long, int> foo; 

instead , cast iterators long long?

no, is, in general, not possible. while pointers can cast , integer types (more on later), iterators aren't pointers , cast isn't allowed. example, consider istream_iterator, wraps stream object. it's unclear mean cast or long long. if you're trying solve problem way, may need change approach.

as note - type long long not required big enough hold pointer that's been converted integer. special types intptr_t , uintptr_t guaranteed big enough store pointer, might want start using types instead. still can't cast list iterators these types, though.