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#stdlib
- v
voddan
06/21/2016, 2:25 PMmine does the same , no? - c
cedric
06/21/2016, 2:26 PMAren't there two loops in your code? - v
voddan
06/21/2016, 2:27 PMI guess there is, but your code does not copy
, which I needvalue - v
voddan
06/21/2016, 2:27 PMif you fix your example, they will be exactly the same - i
ilya.gorbunov
06/21/2016, 2:39 PMhttps://kotlinlang.slack.com/archives/stdlib/p1466518603000059 Standard maps usually have their map entries already materialized, though it may be not true for some specialized implementations. - v
voddan
06/21/2016, 2:43 PMtrue, thank you! - d
dimsuz
06/22/2016, 9:00 AMhi everyone. there's an
constructor withArray
so I can doinit
. Is there something similar for initializing lists inArray(5, { i -> createItem(i) })
? none ofstdlib
overloads has any additional parameters...listOf - d
dimsuz
06/22/2016, 9:03 AMoh, or I could just use(0..size-1).map { i -> createItem(i) } - k
kirillrakhman
06/22/2016, 9:47 AMit's not as efficient because you need to allocate an additionalIntRange - k
kirillrakhman
06/22/2016, 9:48 AMbtw, if you have a
, you can also doListindices.map { createItem(it) } - k
kirillrakhman
06/22/2016, 9:48 AMor(0..lastIndex).map { ...} - k
kirillrakhman
06/22/2016, 9:49 AMin any case, writing
feels un-Kotlin-y and I try to avoid it when I cansize - 1👍 2 - d
dimsuz
06/22/2016, 10:00 AMagreed. in my case I just found that
was using another list under the hood, so I just went withcreateItem()anotherList.map { ... } - r
rocketraman
06/22/2016, 2:49 PMCan I use
withfilterIsInstance
somehow? I want to filter my list usingwithIndex
but maintain the original index in the resulting `IndexedValue`sfilterIsInstance - v
voddan
06/22/2016, 2:50 PMlist.mapIndexed {i, v -> Pair(i, v)}.filter {it.second is A} as List<Int, A> - r
rocketraman
06/22/2016, 2:54 PMI need a
at the end there to convert themap
into aList<Int, A>
as well. Should work but not so elegant.List<IndexedValue<A>> - v
voddan
06/22/2016, 2:56 PMmy badList<Pair<Int, A>> - v
voddan
06/22/2016, 2:57 PMno idea what IndexedValue is - r
rocketraman
06/22/2016, 2:58 PMTaking your suggestion and codifying it (not tested yet):Copy codefun <T> List<T>.filterIsInstanceIndexed(): List<IndexedValue<T>> = mapIndexed {i, v -> Pair(i, v)}.filter { it.second is T }.map { IndexedValue(it.first, it.second) } - r
rocketraman
06/22/2016, 2:58 PM - v
voddan
06/22/2016, 2:58 PMwhy do you use
if you needPair
?IndexedValue - r
rocketraman
06/22/2016, 2:59 PMYeah I just realized that - v
voddan
06/22/2016, 2:59 PMand you need a cast anyway - r
rocketraman
06/22/2016, 2:59 PMCopy codefun <T> List<T>.filterIsInstanceIndexed(): List<IndexedValue<T>> = mapIndexed {i, v -> IndexedValue(i, v)}.filter { it.value is T } - r
rocketraman
06/22/2016, 2:59 PMNo cast needed it seems, at least according to IJ - v
voddan
06/22/2016, 2:59 PMthanks, didn't know about IndexedValue - v
voddan
06/22/2016, 3:00 PMbecauseList<T> - r
rocketraman
06/22/2016, 3:01 PMOh yeah forgot the class parameter - i
ilya.gorbunov
06/22/2016, 3:07 PMIt's a class in the standard library - r
rocketraman
06/22/2016, 3:08 PMHere we go:Copy code@Suppress("UNCHECKED_CAST") fun <R> Iterable<*>.filterIsInstanceIndexed(clazz: Class<R>): List<IndexedValue<R>> = mapIndexed {i, v -> IndexedValue(i, v)} .filter { clazz.isInstance(it.value) } as List<IndexedValue<R>>