Is there no overhead calling `toMutableList ` again after ma kotlinlang #getting-started

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getting-started

Title

t

tjohnn

08/01/2019, 10:53 AM

Is there no overhead calling

toMutableList()

again after mapping?

m

marstran

08/01/2019, 11:03 AM

~~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.~~

t

tjohnn

08/01/2019, 11:05 AM

Okay I see

s

spand

08/01/2019, 11:27 AM

Collection<T>.toMutableList()

always copies

If you want to end up with something else than a

List

then I suggest you use

mapTo()

m

marstran

08/01/2019, 11:37 AM

Oh, it does? That's weird.

k

karelpeeters

08/01/2019, 12:07 PM

Because you can use a

MutableList

as a

List

it would be pretty weird if it only sometimes copied.

m

marstran

08/01/2019, 12:15 PM

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

t

tjohnn

08/01/2019, 12:33 PM

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

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