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Title
d

diesieben07

08/03/2018, 11:50 AM
I want to split a list into parts based on a condition. Example: Split on even numbers:
val input = listOf(4, 1, 1, 3, 2, 5, 2)
val output = input.chunkedBy { it % 2 == 0 } // should be: [[4, 1, 1, 3], [2, 5], [2]]
Is there such a thing in the standard library?
🇳🇴 1
n
d

diesieben07

08/03/2018, 11:53 AM
groupBy
returns a Map though
n

nfrankel

08/03/2018, 11:56 AM
true
but it’s then quite easy to get its values and put it into a list (or an array)
s

spand

08/03/2018, 11:56 AM
.values
or do you absolutely need a
List
?
d

diesieben07

08/03/2018, 11:57 AM
Yes, I need a list. And I also need the order preserved.
groupBy does not help me here at all, it stuffs things into a bag by a condition
I need to split based on a condition.
n

nfrankel

08/03/2018, 11:59 AM
ok then sorry, i don’t know the stdlib well enough to help you there
😞
d

diesieben07

08/03/2018, 11:59 AM
That's okay
n

nfrankel

08/03/2018, 12:00 PM
chunked()
is based on size...
seems like it should work for you
s

spand

08/03/2018, 12:02 PM
I guess
fold
is the closest you can get
d

diesieben07

08/03/2018, 12:02 PM
partition
only checks a boolean condition
r

rrader

08/03/2018, 1:39 PM
condition only boolean can be
val input = listOf(4, 1, 1, 3, 2, 5, 2)
println(input.partition({ it % 2 == 0 }))
d

diesieben07

08/03/2018, 1:41 PM
That does not do what I want even remotely.
It shoves all even numbers in one list and uneven ones in the other. That is not what I need.
r

rrader

08/03/2018, 1:42 PM
but what do you need? in message you wrote "Split on even numbers"
d

diesieben07

08/03/2018, 1:43 PM
See example input->output above...
r

rrader

08/03/2018, 1:44 PM
and what is condition in that example?
d

diesieben07

08/03/2018, 1:44 PM
It specifies the element to split on
Every even number should "start a new list"
r

Richard Green

08/03/2018, 1:51 PM
What if the first n elements (n>0) are not true for the condition?
if one simplifies it to (t)rue and (f)alse, then is the output of the form (f*)(tf*)* ?
f

fitzoh

08/03/2018, 2:23 PM
so basically a repeated
takeWhile
d

diesieben07

08/03/2018, 2:24 PM
Correct
What if the first n elements (n>0) are not true for the condition?
Then they would be in their own group. I want behavior "like String.split".
k

karelpeeters

08/03/2018, 2:34 PM
condition.invoke(it)
->
condition(it)
d

diesieben07

08/03/2018, 2:42 PM
thats exactly what I wrote for myself 😄
except i used for..in
k

karelpeeters

08/03/2018, 2:43 PM
Out of interest, what is the use case?
d

diesieben07

08/03/2018, 2:49 PM
Parsing a terrible XML document. I get a list of text blocks intermitted with <audio> elements. The <audio> elements specify which audio file to use for the following text blocks.
h

hho

08/03/2018, 2:49 PM
@karelpeeters Fixed. But as I said: It's ugly.
d

diesieben07

08/03/2018, 2:49 PM
I want to parse it into groups of audio+list of text