On Fri, Aug 20, 2010 at 5:22 PM, B Hart <bhartsb@gmail.com> wrote:
well assuming an unsigned int array size of 5 what do you suggest for a reasonably good and fast hash?
I was hoping that I could use the built in hash w/o having to invent one.
boost::hash is actually very nicely extensible. It works with a number of containers (I was surprised it didn't support boost::array (or std::array) out of the box), and adding support for something like boost::array is pretty trivial. See below: #include <boost/array.hpp> #include <boost/functional/hash.hpp> #include <boost/unordered_set.hpp> typedef boost::array<int, 5> Array; namespace boost { template <typename T, std::size_t N> std::size_t hash_value(const boost::array<T,N>& arr) { return boost::hash_range(arr.begin(), arr.end()); }} int main(int argc, char* argv[]) { Array arr1 = {1000, 3344455, 12455222, 8832232, 1234}; Array arr2 = {2000, 4344455, 22455222, 16832232, 2345}; boost::unordered_set<Array> mySet; mySet.insert(arr1); assert(mySet.find(arr2) == mySet.end() && "Found wrong array"); assert(mySet.find(arr1) != mySet.end() && "Not finding correct array"); return 0; } HTH, Nate