Overload macro as variable and function-CodePudding

First, there are a lot of posts on overloading macros:

However, all of them ask the question about variadic macros.

What I'd like to ask is if the following is possible:

#define FOO 3
#define FOO(a,b) a b

int main() {
  int a = FOO(0,1);
  int b = FOO;
  std::cout << a   b;
  return 0;
}

I'd like for it to work on clang as well.

CodePudding user response：

No, macros aren't that clever. They are a simple text substitution, performed by the pre-processor.

At the expense of one more set of brackets you can overload functions though, something like:

int foo () { return 3; }
int foo (int a, int b) { return a   b; }

int main ()
{
    int a = foo (0, 1);
    int b = foo ();
}

And if you want your foos to work with a wider set of types, make them templates.

CodePudding user response：

It's not a macro, but looks like it

struct SmartMacro {
    constexpr operator int() const noexcept { return 3; }
    constexpr int operator()(int a, int b) const noexcept { return a   b; }
};
constexpr SmartMacro FOO;

int main() {
    int a = FOO(0,1);
    int b = FOO;
    std::cout << a   b;
    return 0;
}