Could a variable of Data be used as a map key?
struct Data {
Data(int X, int Y) {x=X; y=Y;}
int x; int y;
}
int main()
{
std::map<Data, int> map_;
map_.insert(std::make_pair(Data(1,2), 0)); //error inserting
}
views:
58answers:
2
+7
A:
Yes, but you either need to define operator< for the class type or use a custom comparison function for the std::map.
There is an example of using a custom comparison function in the STL documentation.
James McNellis
2010-06-23 14:37:34
+1 for suggesting the comparison functor, too many times it does not make sense to define `operator<`.
Matthieu M.
2010-06-23 17:00:40
+1 from me as well for same reason. It might also be useful to point out that std::pair already provides this.
2010-06-25 06:49:08
+1
A:
if you don't want an operator<, you can use boost::unordered_map.
Alexandre C.
2010-06-23 14:47:56