初始化：
std::pair<int, float> p; //initialize p.first and p.second with zero
std::pair<int, const char*> p(42, "hello");
make_pair(42, "hello"); // no need for the var name, it‘s returned by make_pair
make_pair<int, float>(42, "hello");
原文：http://www.cnblogs.com/dracohan/p/3853674.html