Requirements for elements in std::unordered_set

Question

std::unordered_set<my_type> my_set;

Which requirements must my_type fulfill here? (Besides a specialization for std::hash)

Answer 1

You need a specialization for std::hash, and you need an operator == defined to handle hash collisions.

EDIT: You should also make sure your type has a copy constructor (or let the compiler generate one for you) because STL containers have value semantics.

EDIT2: as an example of how to do this, you can check out this other SO answer.