First problem: You are passing string as the second template argument for your instantiation of the unordered_set<> class template. The second argument should be the type of your hasher functor, and std::string is not a callable object. Perhaps meant to write: unordered_set<Interval, /* string */ Hash> test; // ^^^^^^^^^^^^ // Why this? Also, I would … Read more
This works on gcc 4.5 allowing all c++0x tuples containing standard hashable types to be members of unordered_map and unordered_set without further ado. (I put the code in a header file and just include it.) The function has to live in the std namespace so that it is picked up by argument-dependent name lookup (ADL). … Read more
You are expressly allowed and encouraged to add specializations to namespace std*. The correct (and basically only) way to add a hash function is this: namespace std { template <> struct hash<Foo> { size_t operator()(const Foo & x) const { /* your code here, e.g. “return hash<int>()(x.value);” */ } }; } (Other popular specializations that … Read more
The key of the set is declared as being a pointer-to-int, an int*. But this: void push( const B& b ) { set.insert( &b.x ); } is passing the address of a constant int, an int const*, hence the compiler error. Removing the const from the argument would resolve the compiler error, as would making … Read more