Iteration in C

Hi there /prog/.

I know Python, and I'm learning C. Both langs have for loops. Python's nicely iterates over a collection of unknown length. C's usually has you specify the length of the collection at compile time, but what if the length is unknown?

My best newbie guess: you terminate the collection with NULL, or you write an iteration function that returns some end-of-collection value when it's done.

Depends on the data structure. Usually with unknown length you're iterating through a linked list, which terminates when the pointer to the next item is null.

Null termination is one option, another is to store the length as the first element of the array.

>>7
I prefer to store it as the last element of the array, with the i!=arr[i] test.

>>11
It's almost better than using the zeroth element--which is the worst of intelligible solutions. I'd be happier using arr[-1].