Using functions in C++ (void, double, int) - c++

Question

I am slowly trying to learn c++ on my own and got stuck using functions. I did find a way to get past the initial problem but I have no idea why I couldn't do it the way I first intended to. Here's the working program.
// ex 6, ch 2
#include <iostream>
using namespace std;
void time(int, int);
int main()
{
int h, m;
cout << "Enter the number of hours: ";
cin >> h;
cout << endl;
cout << "Enter the number of minutes: ";
cin >> m;
cout << endl;
time(h, m);
cin.get();
cin.get();
return 0;
}
void time(int hr, int mn)
{
cout << "The time is " << hr << ":" << mn;
}
And here is how I would like to do it.
// ex 6, ch 2
#include <iostream>
using namespace std;
void time(int, int);
int main()
{
int h, m;
cout << "Enter the number of hours: ";
cin >> h;
cout << endl;
cout << "Enter the number of minutes: ";
cin >> m;
cout << endl;
cout << "The time is " << time(h, m);
cin.get();
cin.get();
return 0;
}
void time(int hr, int mn)
{
cout << hr << ":" << mn;
}
In my head both of them would return the same thing but my compiler thinks otherwise (and I would like to know why).
Edit: It seems to work like this for some odd reason.
cout << "The time is ";
time(h, m);
If nothing more, it just made me more confused.

Answer 1

cout << "The time is " << time(h, m);
time does not return anything, but to send something to cout in this case would require it to return a value (probably a string in this case) vs having the time function call cout directly.

Answer 2

You need to edit your time-function to return a string. I'm using stringstream to convert int to string.
#include <sstream>
...
string time(int, int);
...
string time(int hr, int mn)
{
stringstream sstm;
sstm << hr << ":" << mn;
string result = sstm.str();
return result;
}
Now you can use it directly, like:
cout << "The time is " << time(h, m);