Need to return an immutable variable number of items from a function. Should I return a

List<T>

or

Array<T>

?

Array

is always mutable but its size is fixed.

List

is read-only, but if it's backed by a

MutableList

, or another implementation that can change, its size and content may change. The simple answer is to use

List

.

I should also mention I'm passing full ownership to the caller. So if they wish to mutate it, so be it.

full ownership of what?

Of the

List<T>

or

Array<T>

.

And what it means, concretely?

Just emphasizing that when I say immutable, it doesn't matter 😅 . I'm not trying to protect the returned values at all.

Then, if iteration performance is critical or is a hot spot, use

Array

, otherwise, use

List

.

Okay

just use list, even if it's backed by a mutablelist, the exposed type should be list. arrays are easier to mess up from the caller point of view