Making Functions

Question

Currently, I am making a language I would call Supercode (not official) and my base is C. Now, I would like to build this function called take, which acts like a printf & scanf thing. It could act like this:

int main(void) {
int x;
printf("Give us a number: ");
scanf("%i", x);
x *= 2;
printf("x × 2 = %i", x);
}

So that I can make a function that could be like this:

function main() {
take(int, x, "Give us a number: ");
x += *2;
say("# × 2 = " & x);
}

How do I do it?