Hi, I'm using Arrow Optics and I'm trying to modif...

# arrow

[Giorgio Antonioli]

Hi, I'm using Arrow Optics and I'm trying to modify the items of a list based on the list's index. In pseudo code (I even tried with FilterIndex without succeeding):

val lens = MyClass.listProperty
              .every(ListFilterForIndex { index -> index % 2 })
              .itemProperty
var myObject = MyClass()
myObject = lens.modify(myObject) { "modified string" }

[raulraja]

https://arrow-kt.io/docs/optics/index/#example

[Giorgio Antonioli]

@pakoito Nothing fails, I wrote it in pseudo code, so that every isn't a valid code at all

[pakoito]

without succeeding

what isn't working?

[pakoito]

what's not happening?

[Giorgio Antonioli]

I simply don't know which method I can use to modify the items of a list using a lambda for the index instead of using index(ListIndex(), 2) . The line every(ListFilterForIndex { index -> index % 2 }) was invented by myself, it isn't valid, it doesn't even compile since ListFilterIndex doesn't implement Each<T> .

[raulraja]

@simon.vergauwen may know if there is a way

[Giorgio Antonioli]

@simon.vergauwen Understood, thanks very much for your help!