main.cpp

#include <iostream>

using namespace std;

auto returnInt(void) { return 100; }
auto returnString(void) { return "Hello World"; }
auto returnDouble(void) { return 100.5; }

int main(int argc, char *argv[])
{
    cout << returnInt() << endl;
    cout << returnString() << endl;
    cout << returnDouble() << endl;
}