/*
- likely hash map backed, thus O(1) instead of O(log(n)) for set
- uses the std::hash function
http://stackoverflow.com/questions/15869066/inserting-into-unordered-set-with-custom-hash-function
http://en.cppreference.com/w/cpp/utility/hash
- stdlib does not have a hash for tuples... so combining hashes of instance variables is the main question then.
So you just go with `boost::hash_combine` for now...
- http://codereview.stackexchange.com/questions/136770/hashing-a-tuple-in-c17
- http://stackoverflow.com/questions/2590677/how-do-i-combine-hash-values-in-c0x
- http://stackoverflow.com/questions/35985960/c-why-is-boosthash-combine-the-best-way-to-combine-hash-values
- http://stackoverflow.com/questions/3611951/building-an-unordered-map-with-tuples-as-keys
- http://stackoverflow.com/questions/7110301/generic-hash-for-tuples-in-unordered-map-unordered-set
- a custom hash for a class can be given either via constructor, or by embedding into std::
*/
#include "common.hpp"
class MyClass {
public:
int i;
int j;
MyClass(int i, int j) : i(i), j(j) {}
};
bool operator==(const MyClass& lhs, const MyClass& rhs) {
return lhs.i == rhs.i;
}
namespace std {
template <>
struct hash {
std::size_t operator()(const MyClass& k) const {
return k.i;
}
};
}
int main() {
std::unordered_set mySet;
assert(mySet.size() == 0);
mySet.insert(MyClass(1, 2));
assert(mySet.size() == 1);
mySet.insert(MyClass(1, 3));
assert(mySet.size() == 1);
assert(mySet.find(MyClass(1, -1))->j == 2);
}