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What are the main differences between `Iterator` and `Sequence`?

<https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.sequences/-sequence/index.html|https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.sequences/-sequence/index.html>

A Sequence can be transformed into an Iterator, even though it doesn't implement the Iterable interface.

So why is there special class instead of just using Iterable?

Sequences are lazy, non-eager and immutable (no remove() on its Iterator).

Because of this, the hasNext() method of the Iterator from a Sequence may have some side-effects.

`Iterator` in Kotlin has no `remove` either, you would need to implement `MutableIterator`. :wink:

<https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/-mutable-iterator/index.html>

<@U72C3TBDH> does that mean Iterator is eager?

I meant ‘eager’ as the opposite of ‘lazy’. :slightly_smiling_face: