advanced patterns with std::unordered_map and custom hash function in C++11
I'm relatively new to this, so bear with me. Hey everyone, I'm running into an issue that's driving me crazy. I'm sure I'm missing something obvious here, but I'm running into an scenario with my custom hash function while using `std::unordered_map`. I've defined a struct `MyKey` and created a custom hash function for it, but the map seems to be producing unexpected results when I try to retrieve values. Here’s the relevant code snippet: ```cpp #include <iostream> #include <unordered_map> #include <string> struct MyKey { std::string str; int num; bool operator==(const MyKey& other) const { return str == other.str && num == other.num; } }; struct MyKeyHash { std::size_t operator()(const MyKey& k) const { return std::hash<std::string>()(k.str) ^ std::hash<int>()(k.num); } }; int main() { std::unordered_map<MyKey, int, MyKeyHash> myMap; MyKey key1 = {"example", 1}; myMap[key1] = 42; MyKey key2 = {"example", 2}; myMap[key2] = 43; MyKey searchKey = {"example", 1}; std::cout << "Value: " << myMap[searchKey] << std::endl; return 0; } ``` When I run this code, I expect to retrieve `42` for the key `{"example", 1}`, but I get a default-constructed value instead. There are no exceptions or runtime errors, but it seems like the key isn't being found in the map. I've checked the `operator==` method, and it appears to be implemented correctly. I've also verified that the hash values for both `key1` and `searchKey` are identical. It's as if the `unordered_map` isn't recognizing the keys as equal. Is there something subtle I might be missing regarding how `std::unordered_map` handles equality checks or hashing? Any suggestions would be greatly appreciated! My development environment is macOS. Any help would be greatly appreciated! I recently upgraded to Cpp latest. Thanks for taking the time to read this! I'm open to any suggestions. Thanks in advance!