Now, let us suppose that expression a has side-effects...

"But that's just stupid!"

Yes. Now, given that a has side-effects...

Assuming a has type int:

  int a_val = a;
  if (a_val)
    printf ("returning b");
  return a_val ? b : c;

Anyway, it's not useful for complicated code that needs to do lots of stuff. It's useful for simple code that ends up being more verbose with if-else. It's also useful for enforcing behaviour.

Suppose I want to `printf("Returning. A: %i", a)`. Same answer.