#include<stdio.h>

int d(int x){
	return x+x;
}

int t(int x){
	return x*3;
}

int main(){
	int x = 10;
	printf("%d doubled is %d\n", x, d(x));

	auto operation = d; // NOT in C, just C++ (sorry)
	printf("%d doubled is %d\n", x, operation(x));

	operation = t;
	printf("%d doubled is %d\n", x, operation(x));
	return 0;
}