Question

From what I understand, the key in a value pair in an std::map cannot be changed once inserted. Does this mean that creating a map with the key template argument as const has no effect?

std::map<int, int> map1;
std::map<const int, int> map2;

Answer 1

The answer to your title question is yes. There is a difference. You cannot pass a std::map<int, int> to a function that takes a std::map<const int, int>.

However, the functional behavior of the maps is identical, even though they’re different types. This is not unusual. In many contexts, int and long behave the same, even though they’re formally different types.