operator as template parameter

Question

Is it possible?

template<operator Op> int Calc(int a, b)
{ return a Op b; }

int main()
{ cout << Calc<+>(5,3); }

If not, is way to achieve this without ifs and switches?

Answer 1

You could use functors for this:

template<typename Op> int Calc(int a, int b)
{
    Op o;
    return o(a, b);
}

Calc<std::plus<int>>(5, 3);

Answer 2

No - templates are about types or primitive values.

You can nontheless pass so called function objects that can be called like functions and carry the desired operator functionality (despite having a nice syntax).

The standard library defines several ones, e.g. std::plus for addition ...

#include <functional>

template<typename Op>
int Calc(int a, int b, Op f) { 
  return f(a, b);
}

int main() { 
  cout << Calc(5,3, std::plus());
  cout << Calc(5,3, std::minus());
}