please tell me when multiple varibles are returned which one gets stored?

Question

I came across this code and want to know what this line [X] will it return:

int add_multiply(int a, int b)
{
  int p, q;
  p = a + b;
  q = a * b;
  return (p, q); //X
}
void main()
{
  int b, a = add_multiply(1, 2);
  b = add_multiply(3, 4);
  printf("%d%d", a, b);
}

Always the last one. Also, don't use void main(). thats ugly. — Magisch, Apr 08 '16 at 11:52
@Magisch Nonsense, there is nothing wrong with `void main` in a generic C context, [see this](http://stackoverflow.com/a/31263079/584518). — Lundin, Apr 08 '16 at 11:57

haccks · Answer 1 · 2016-04-08T12:46:26.223

7

You can't return more than one variable at once from a function in C. The statement

return(p, q); // or return p, q;

returns q only. The , in p, q is a comma operator. p will be evaluated and it's value will be discarded, then q will be evaluated and then its value will be returned.

edited Apr 08 '16 at 12:46

answered Apr 08 '16 at 11:50

haccks

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You could add that's because `return` IS NOT A FUNCTION and he would get the same result with `return p, q;`. – jdarthenay Apr 08 '16 at 11:59
Why is `return(p, q)` equal to `return p, q`? I mean, `int a; a = (5, 6);` and `int a; a = 5, 6;` are different... – Spikatrix Apr 08 '16 at 12:34
1

@CoolGuy; In `a = 5, 6;`, expression will be evaluated as `(a = 5), 6;` while in `return p, q` it will be `return (p, q)`. – haccks Apr 08 '16 at 12:39
@haccks So, there is no way to return `p` using the comma operator in the `return` statement? – Spikatrix Apr 08 '16 at 13:11
@CoolGuy; Yes, there is: `return q, p;` :) – haccks Apr 08 '16 at 13:19

please tell me when multiple varibles are returned which one gets stored?

1 Answers1