Question

Is there a way to do complex copy from a map<A,B> to cout, use C++’s copy function ?

Seems complicated, since map has more than one item, and iterator itself doesn’t point to read data.

I mean something like what we do with vector:

copy (vector.begin(), vector.end(), ostream<int>(cout," "));

Answer 1

The value_type of a map is a std::pair<key_type, assoc_type>. To do a copy, you need to provide an operator<< that takes that type. For example, for a map<string, int>, it would be:

std::ostream *operator<<(std::ostream &os, std::pair<std::string, int> const &v) {
    return std::cout << v.first << ":\t" << v.second;
}

You usually have to put that inside namespace std for the compiler to find it though.