C++0x adds hash<...>(...).
I could not find a hash_combine function though, as presented in boost. What is the cleanest way to implement something like this? Perhaps, using C++0x xor_combine?
views:
149answers:
1
+4
A:
Well, just do it like the boost guys did it:
template <class T>
inline void hash_combine(std::size_t& seed, const T& v)
{
std::hash<T> hasher;
seed ^= hasher(v) + 0x9e3779b9 + (seed<<6) + (seed>>2);
}
Polybos
2010-04-07 19:18:41
yeah, that's the best I could do too. I don't understand how the standards committee declined something so obvious.
Neil G
2010-04-07 23:00:59
@Neil: I agree. I think a simple solution for them would be the requirement of the library to have a hash for `std::pair` (or `tuple`, even). It would compute the hash of each element, then combine them. (And in the spirit of the standard library, in an implementation defined way.)
GMan
2010-04-08 06:06:04
There are a lot of obvious things omitted from the standard. The process of intensive peer review makes it difficult to get those little things out the door.
2010-06-27 08:38:40