isLast

Islast is a boolean predicate used in programming to determine whether the current element in an ordered sequence is the last one. The term is often encountered as a function named isLast, a method, or a contextual flag in libraries, templates, or utility modules; it is not a universal primitive found in all languages, but the idea appears wherever sequential iteration occurs.

Common ways to implement isLast include: using the known length of a collection and comparing the current index to length minus one; or for iterables with unknown length, employing a lookahead strategy that fetches the next element before or while processing the current one, and treating the final fetched item as the last. In Python-like pseudocode, one might write: for i, x in enumerate(seq): is_last = (i == len(seq) - 1). In a streaming loop with lookahead, you can fetch the first element, process previous ones with is_last set to false, and after the loop process the final element with is_last set to true.

Uses for isLast include controlling formatting (such as rendering separators only between items), conditional rendering in templates, and algorithms that need a special case for the final element. It is particularly helpful for avoiding unnecessary checks inside tight loops, but it can introduce extra complexity or memory overhead if length is precomputed or if lookahead is required for every iteration.

See also: last, length, iterators, lookahead, enumeration.