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kotlinlang

Is there no overhead calling `toMutableList()` again after mapping?

~Depends on the actual type of list. If the list is already mutable, then there's no overhead. If it's not, then it copies all elements to a mutable list.~

`Collection&lt;T&gt;.toMutableList()` always copies

If you want to end up with something else than a `List` then I suggest you use `mapTo()`

Because you can use a `MutableList` as a `List` it would be pretty weird if it only sometimes copied.

Yeah, nevermind. The not-copying optimization would only make sense for immutable lists.

Hmm.. why I wanted to avoid it earlier. Thanks.