How can I use custom keys in std::map with C++17?

How can I use custom keys in std::map with C++17?

In C++17, you can use custom keys in std::map by defining a struct or class and providing a comparison operator.

Can you show me an example of a custom key?

Sure! Here's a simple example:

struct CustomKey {
    int id;
    std::string name;

    bool operator<(const CustomKey& other) const {
        return id < other.id;
    }
};

std::map<CustomKey, std::string> myMap;

What if I want to use multiple fields for comparison?

You can modify the comparison operator to compare multiple fields. For example:

bool operator<(const CustomKey& other) const {
    if (id != other.id) return id < other.id;
    return name < other.name;
}

Is there a way to use std::hash with custom keys?

Yes, you can use std::unordered_map with custom keys by providing a hash function. You need to define a struct for the hash function.