How do I avoid implicit conversions on non-constructing functions?

Question

How do I avoid implicit casting on non-constructing functions?
I have a function that takes an integer as a parameter,
but that function will also take characters, b

Answer 1

Here's a general solution that causes an error at compile time if function is called with anything but an int

template 
struct is_int { static const bool value = false; };

template <>
struct is_int { static const bool value = true; };


template 
void function(T i) {
  static_assert(is_int::value, "argument is not int");
  return;
}

int main() {
  int i = 5;
  char c = 'a';

  function(i);
  //function(c);

  return 0;
}

It works by allowing any type for the argument to function but using is_int as a type-level predicate. The generic implementation of is_int has a false value but the explicit specialization for the int type has value true so that the static assert guarantees that the argument has exactly type int otherwise there is a compile error.