Get access to the data stored in iterator

Question

I'm trying to get more comfortable with std::multiset and std::pair. So I wrote a little main program which creates a multiset and pushes elements into it, as you can see below.

#include <set>
#include <utility>
#include <iostream>
#include <string>

int main()
{
    std::cout << "Hello World" << std::endl;

    /*
    std::multiset<std::pair<int, float> > set;
    std::multiset<std::pair<int, float> >::iterator it;
    set.insert(std::make_pair(534, 5.3));
    set.insert(std::make_pair(22, 9.2));*/

    std::multiset<int> set;
    std::multiset<int>::iterator it;
    set.insert(43);
    set.insert(45);
    set.insert(32);

    for(it = set.begin(); it != set.end(); it++)
    {
        std::cout << *it << std::endl;
    }
    std::cout << "Bye" << std::endl;
    return 1;
}

When I create an int-multiset everything works fine. But when I comment the second multiset-block out and use the first one instead. I get following compile error:

std::cout << *it << std::endl;no match for 'operator<<' (operand types are'std::ostream {aka std::basic_ostream<char>}' and 'const std::pai<int, float>')

So I replaced

std::cout << *it << std::endl;

with

std::cout << *it.first << std::endl;

and get following error:

‘std::multiset<std::pair<int, float> >::iterator {aka struct std::_Rb_tree_const_iterator<std::pair<int, float> >}’ has no member named ‘first’

How can I fix this, to get access to the first value of the std::pair element stored inside the multiset?

Answer 1

Due to operator precedence, you essentially wrote *(it.first). You can use parenthesis to specify the order you want the operators to resolve :

std::cout << (*it).first << std::endl;

Though you can just use operator-> instead :

std::cout << it->first << std::endl;