Template function only works with VS

Question

I have written a code with template but it works only with Visual Studio( not in Dev c++ or any online compiler. I don't understand why.

#include <iostream>
using namespace std; 

template <class Q1,class Q2,class Q3> // but when i write instead of 3 classes  1 class it will work 
                                      //everywhere, how could it be possible?

void min(Q1 a, Q2 b, Q3 c) {
    if (a <= b && a <= c) { 
        cout << "\nMinimum number is: " << a << endl; }
    if (b < a && b < c) {
        cout << "\nMinimum number is: " << b << endl; }
    if (c < a && c < b) { 
        cout << "\nMinimum number is: " << c << endl; }

}

int main()
{

    double x,y,z;
    cout << "Enter 3 numbers: " << endl;
    cin >> x;
    cin >> y;
    cin >> z;

    min(x, y, z);
}

`using namespace std;` - remove this and type `std::` where needed. `std::min` is a thing, you don't want name conflicts. — Mat, Nov 13 '19 at 16:59
The compiler cannot distinguish between your function and [`std::min`](https://en.cppreference.com/w/cpp/algorithm/min). It just happens that MSVC didn't `#include ` within `iostream`, but other compilers did (and they are perfectly allowed to do so). — Yksisarvinen, Nov 13 '19 at 17:01
Yep, or change it to `::min(x, y, z)`. Your own function is conflicting with `std::min` and this is a good example why `using namespace` is bad. — Lukas-T, Nov 13 '19 at 17:02
@churill soyou mean if I remove _using namespace_ it will work? — , Nov 13 '19 at 17:05

score 3 · Accepted Answer · answered Nov 13 '19 at 17:05

The function std::min is used implicitly. That's because overload resolution favours non-template functions over template ones, and some compiler toolsets allow std::min to be reachable via the #includes you have (the only thing the C++ standard has to say on the matter is that std::min must be available once #include <algorithm> is reached).

Dropping using namespace std; is one fix, and is a good idea anyway. Tutorials often use it for clarity, but it's rare to find it in production code.

Template function only works with VS

1 Answers1