#include <iostream>
 
#define COUNT_N(_1, _2, _3, _4, _5, _6, _7, _8, _9, _10, N, ...)    N
#define COUNT(...)   COUNT_N(__VA_ARGS__, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1)
// Warning: COUNT() return 1 (as COUNT(A)) :-/
 
#define IDENTITY(N) N
#define APPLY(macro, ...) IDENTITY(macro(__VA_ARGS__))
 
#define F_1(a) functionBeingUsed(); a;
#define F_2(a, b) functionBeingUsed(a); b;
#define F_3(a, b, c) functionBeingUsed(a, b); c;
#define F_4(a, b, c, d) functionBeingUsed(a, b, c); d;
#define F_5(a, b, c, d, e) functionBeingUsed(a, b, c, d); e;
#define F_6(a, b, c, d, e, f) functionBeingUsed(a, b, c, d, e); f;
#define F_7(a, b, c, d, e, f, g) functionBeingUsed(a, b, c, d, e, f); g;
#define F_8(a, b, c, d, e, f, g, h) functionBeingUsed(a, b, c, d, e, f, g); h;
 
#define DISPATCH(N) F_ ## N
 
#define Macro(...) IDENTITY(APPLY(DISPATCH, COUNT(__VA_ARGS__)))(__VA_ARGS__)
 
void functionBeingUsed(int a, int b, int c) { std::cout << "hello world 3\n"; }
void functionBeingUsed(int a, int b, int c, int d) { std::cout << "hello world 4\n"; }
 
int main() {
    Macro(1,2,3,4, int i = 0);
    Macro(1,2,3, int j = 0);
}
 
 

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