A basic Hashmap class for C++.

insert(Key key, Value value) : Inserts a key-value pair into the hashmap.
erase(Key key) : Erases a key-value pair from the hashmap. If the given key is found, it returns true, else false.
clear(Key key) : Clears the contents of the hashmap.
operator[](Key key) : Returns a reference to the Value associated with the Key provided as an argument. If the key is not found, it will return a reference to a value-initialised variable of type Value.

The user can optionally provide a pointer to a hash function in the constructor. The return type must be of type size_t, and there must be a single argument of the template type Key.