What's a good way to structure variable nested loops?

Question

Suppose you\'re working in a language with variable length arrays (e.g. with A[i] for all i in 1..A.length) and have to write a routin

Answer 1

Since they were opposed to recursion (don't ask) and I was opposed to messy case statements (which, as it turned out, were hiding a bug) I went with this:

procedure register_combination( items : vararray of vararray of An_item)
    possible_combinations = 1
    for each item_list in items
        possible_combinations = possible_combinations * item_list.length
    for i from 0 to possible_combinations-1
        index = i
        this_combination = []
        for each item_list in items
            item_from_this_list = index mod item_list.length
            this_combination << item_list[item_from_this_list]
            index = index div item_list.length
        register_combination(this_combination)

Basically, I figure out how many combinations there are, assign each one a number, and then loop through the number producing the corresponding combination. Not a new trick, I suspect, but one worth knowing.

It's shorter, works for any practical combination of list lengths (if there are over 2^60 combinations, they have other problems), isn't recursive, and doesn't have the bug.