feat: introduce takeLast(n) operator
#31
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| * }}} | ||
| */ | ||
| def takeLast(n: Int): List[T] = | ||
| require(n > 0, "n must be > 0") |
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thought: Isn't 0 a legal case as well, where we would return an empty list? We'd probably need to drain the source then to make the side effects "compatible" with calling takeLast with n > 0.
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Akka Streams requires n > 0. On the other hand, I don't see anything wrong with your idea @rucek.
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OK, that was probably the inspiration. On the other hand, Scala collections use n.max(0) - although I'm aware that collections might have different semantics than streams/channels. My own issue with allowing 0 for takeLast is that it might require "artificially" draining the channel (so that it has a similar side effect on the channel to calling takeLast with n > 0) - I'm not sure if it's a correct approach.
@adamw any thoughts?
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Nil + drain sounds most reasonable I guess :)
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Added the case when n == 0 to implementation and unit tests.
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Returns the list of up to `n` last elements from this source. Less than `n` elements is returned when this source contains les elements than requested. The [[List.empty]] is returned when `takeLast` is called on an empty source. Example: Source.empty[Int].takeLast(5) // List.empty Source.fromValues(1).takeLast(0) // List.empty Source.fromValues(1).takeLast(2) // List(1) val s = Source.fromValues(1, 2, 3, 4) s.takeLast(2) // List(4, 5) s.receive() // ChannelClosed.Done
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Returns the list of up to
nlast elements from this source. Less thannelements is returned when this source contains les elements than requested. The [[List.empty]] is returned whentakeLastis called on an empty source.Example: