Enumerators & Lazy Evaluation

A blockless iterator returns an Enumerator

You saw it in module 25: call each (or map, select, …) without a block and you get back an Enumerator — an object that has captured "how to iterate" and can be driven later. This is why arr.each.with_index and arr.map.with_index work: the blockless call returns an Enumerator, and with_index chains onto it.

In an interview, say: "Calling an iterator without a block returns an Enumerator — a paused, resumable iteration you can chain (with_index, with_object) or pull one-at-a-time with next. It decouples how to iterate from what to do."