How would one implement Lazy Evaluation in C?

Question

Take for example,

The follow python code:

def multiples_of_2():
  i = 0
  while True:
    i = i + 2
    yield i

How do we translate thi

Answer 1

As Will mentioned, languages like python do the job of storing the state of the stack between successive calls of the generator. Since C does not have this mechanism, you'll have to do it yourself. The "generic" way of doing this is not for the faint-hearted, as Greg pointed out. The traditional C way of doing this would be for you to define and maintain the state yourself and pass it in and out of your method. So:

struct multiples_of_two_state {
       int i;
       /* all the state you need should go in here */
};

void multiples_of_two_init(struct multiples_of_two_state *s) {
    s->i = 0;
}

int multiples_of_two_next(struct multiples_of_two_state *s) {
    s->i += 2;
    return s->i;
}

/* Usage */
struct multiples_of_two_state s;
int result;
multiples_of_two_init(&s);
for (int i=0; i