4. std::pair structure

std::pair< T1, T2 >

is a C++ structure that holds one object of type T1 and another one of type T2:

    #include <cassert>
    #include <string>
    #include <utility>
    using namespace std;
    int main (int argc, char* argv[])
    {
        pair< string, string > strstr;
        strstr.first = "Hello";
        strstr.second = "World";

        pair< int, string > intstr;
        intstr.first = 1;
        intstr.second = "one";

        pair< string, int > strint( "two", 2 );
        assert( strint.first == "two" );
        assert( strint.second == 2 );

        return 0;
    }

A pair is much like a container that holds exactly two elements.

The pair is defined in the standard header named utility.