Channels
#stdlib
- j
jw
08/04/2016, 7:29 PM
hasMutableList
for thatset - r
rocketraman
08/04/2016, 7:30 PMI want to operate on
, returning a new read-onlyListList - j
jw
08/04/2016, 7:30 PMgot it - j
jw
08/04/2016, 7:32 PMi wouldn't mind seeing something like
so that you doinline fun <T> List<T> transform(f: MutableList<T>.() -> Unit): List<T>
because you could also chain multiple mutable operators inside that lambdalist.transform { set(0, foo) }👍 1 - j
jw
08/04/2016, 7:32 PMor just call itmutate - r
rocketraman
08/04/2016, 7:33 PMNice - j
jw
08/04/2016, 7:34 PMit's not as terse as your function for this use case, but its more generally applicable - r
rocketraman
08/04/2016, 7:35 PMYup - r
rocketraman
08/04/2016, 7:41 PMYour approach supports operations like:set(index, get(index).let { it.copy(...) }) - i
ilya.gorbunov
08/04/2016, 8:57 PMThere will be function
for immutable list. Also itsfun <T> ImmutableList<T>.mutate((MutableList<T>) -> Unit): ImmutableList<T>
function has the signature as @rocketraman asking:set
. Not sure, we should have something like for read-only lists though.fun set(index: Int, element: E): ImmutableList<E> - r
rocketraman
08/04/2016, 8:59 PMGreat! Why not
for read-only list as well?mutate - i
ilya.gorbunov
08/04/2016, 9:09 PMThis may incur too much defensive copying if we're going to protect against
instance passed to the lambda leaking somewhere outside.MutableList - r
rocketraman
08/04/2016, 9:11 PMAh right, makes sense - h
hastebrot
08/08/2016, 9:15 AMFacebook's
has aimmutable.js
function (https://facebook.github.io/immutable-js/docs/#/Seq/cacheResult).Seq.cacheResult()If you know a Seq will be used multiple times, it may be more efficient to first cache it in memory.
Use this method judiciously, as it must fully evaluate a Seq which can be a burden on memory and possibly performance.
- h
hastebrot
08/08/2016, 9:16 AM - m
mbickel
08/08/2016, 9:30 AMDoesn't this violate the substitution principle? - h
hastebrot
08/08/2016, 9:40 AM@mbickel: What exactly would violate LSP? - m
mbickel
08/08/2016, 9:42 AMCan't do this on an infinite sequence, right? - h
hastebrot
08/08/2016, 9:57 AMYes, that's true. - h
hastebrot
08/08/2016, 9:58 AMIt's not the best solution. - h
hastebrot
08/08/2016, 10:01 AMThis is my solution for another problem. Also not the best solution.
(i.e.iterator()
) introduces mutability.it - d
dimsuz
08/08/2016, 12:03 PMis there an stdlib function to find an index of the key in a LinkedMap? - a
artem_zin
08/08/2016, 12:53 PM@dimsuz: what about:Copy codelinkedMap.toList().indexOfFirst { condition } - d
dimsuz
08/08/2016, 12:54 PMthat would work, didn't think of it, thanks - u
uhe
08/08/2016, 1:00 PMthat always creates a list though - u
uhe
08/08/2016, 1:03 PM
should also worklinkedMap.entries.indexOfFirst { condition }👍 2 - d
dimsuz
08/08/2016, 1:34 PMthanks - d
dimsuz
08/08/2016, 3:10 PManother question: 1. I have a
class property 2. I do not (or can not) use delegates.lazy for whatever reason Is there some idiomatic way to say:var map: Map<K,V>? = nullCopy code
or is this the same as with java? I know I could use apply/let stuff here, but dunno if this is the wayif(map == null) { map = mutableMapOf() } map.doSomething() - v
vmironov
08/08/2016, 3:11 PMmap.orEmpty().doSomething()