autohell.cpp

[ecko@work cpp]$ cat autohell.cpp
#include <iostream>

auto add(auto x, auto y)
{
    return x + y;
}

struct pt {
    float _x, _y;
    pt(float x, float y) : _x(x), _y(y) {}
    pt operator+(const pt& v) const { return pt(_x + v._x, _y + v._y); }
};

std::ostream& operator<<(std::ostream& os, const pt& v)
{
    os << "pt(" << v._x << ',' << v._y << ')';
    return os;
}

int main()
{
    std::cout
        << add(5,2) << ' '
        << add(5.0, 3.4) << ' '
        << add(pt(1,2), pt(3,4)) << std::endl;
    return 0;
}
[ecko@work cpp]$ ninja autohell && ./autohell
[1/1] CXXLD autohell
autohell.cpp:3:10: warning: use of ‘auto’ in parameter declaration only available with -fconcepts
 auto add(auto x, auto y)
          ^~~~
autohell.cpp:3:18: warning: use of ‘auto’ in parameter declaration only available with -fconcepts
 auto add(auto x, auto y)
                  ^~~~
7 8.4 pt(4,6)