I have a list of numbers: `val numbers = listOf(1,0,4,0,10,14,16,0,0,34,46)` how can I transform it...

# getting-started

[Daniele B]

I have a list of numbers:
val numbers = listOf(1,0,4,0,10,14,16,0,0,34,46)

how can I transform it in another list where each number is the maximum so far?
val numbers = listOf(1,1,4,4,10,14,16,16,16,34,46)

[randomcat]

You can use `runningReduce`: https://pl.kotl.in/MfM-GN6U1

[Daniele B]

@randomcat thanks!
I think I simplified it too much 🙂
in reality, my list is structured like this:
val numbers = listOf(obj(1),obj(0),obj(4),obj(0),obj(10),obj(14),obj(16),obj(0),obj(0),obj(34),obj(46))
it’s a list of objects,
where the number is one of the object properties
how is it possible to apply the same pattern in case of the object?

[randomcat]

add a map { it.value /* or whatever */ } to get the value out

[Daniele B]

I got stuck.
I am not sure how to use map in this context

[Daniele B]

class MyObj {
val number : Int
}


initial list:

val = listOf(MyObj(1), MyObj(0), MyObj(4), MyObj(0), MyObj(10), MyObj(14), MyObj(16), MyObj(0),obj(0), MyObj(34), MyObj(46))


desired list:

listOf(MyObj(1), MyObj(1), MyObj(4), MyObj(4), MyObj(10), MyObj(14), MyObj(16), MyObj(16), obj(16), MyObj(34), MyObj(46))

[randomcat]

oh, you want to keep the objects, not just the values

[randomcat]

one second

[Daniele B]

yes, exactly

[randomcat]

https://pl.kotl.in/xlRBN5mF2

[Daniele B]

@randomcat thanks again!
however I can see that it replaces the whole object and not just the value of the property
(as I would like).
I have added an extra property and you can see it here:
https://pl.kotl.in/tuvumPXk9

[randomcat]

so which values of the other properties do you want?

[Daniele B]

I would like to keep the same objects, and only update the single property in the objects

[randomcat]

which object do you want the other properties to come from? the first object?

[Daniele B]

so the “id” properties in the example, should stay the same

[Daniele B]

as you can see it’s a list of 5 objects, where each object has two properties: value and id
I would like the “id” to stay the same, and only change the “value”

[randomcat]

where do you want the id to come from?

[Daniele B]

the “id” should stay the same

[randomcat]

it should stay the same at what value?

[Daniele B]

basically, I would like this:
[I(value=1, id=A), I(value=0, id=B), I(value=4, id=C), I(value=0, id=D), I(value=10, id=E)]
to become this:
[I(value=1, id=A), I(value=1, id=B), I(value=4, id=C), I(value=4, id=D), I(value=10, id=E)]

[randomcat]

https://pl.kotl.in/poNQd6Gnb

[Daniele B]

by running the code I get this:
[I(value=1, id=A), I(value=1, id=A), I(value=4, id=C), I(value=4, id=C), I(value=10, id=E)]

[Daniele B]

so, the ID gets changed too

[randomcat]

that's not what I get with the link above

[Daniele B]

that’s weird

[Daniele B]

ok, I did refresh, and it works now, thanks!

[Daniele B]

Ok, I see, you are using “copy”, so you are actually generating a new object.
For efficiency, it would be ideal to just update the value.

[Daniele B]

but I am not sure if in Kotlin it’s possible

[randomcat]

runningReduce doesn't play nice with mutation, and it seems like a bad idea to mutate here

[Daniele B]

ok, I see

[Daniele B]

still, many thanks!