CODEWITHSUNDEEP
kotlin
Heiko
Heiko

Reputation: 159

How to handle elements that fell through a filter when using Sequence in Kotlin

I would like to filter a list and log the items which fell through the filter, similar to this:

val evenNumbers = (1..10)
            .filter { it % 2 == 0 }
            .onFallThrough { println("dropped $it") }  // wishful Kotlin
            .toList()

This should then lead to the following output:

dropped 1
dropped 3
dropped 5
dropped 7
dropped 9

as well as all even numbers collected in the list evenNumbers.

Looking through the manual page on Sequences, I couldn't find anything that seemed to do this. Is there a way to achieve this in Kotlin?

Upvotes: 1

Views: 397

Answers (1)

s1m0nw1
s1m0nw1

Reputation: 82117

I would use partition:

val evenNumbers = (1..10)
    .partition { it % 2 == 0 }
    .let {
        println("dropped ${it.second}")
        it.first
    }

It returns a Pair with its first property containing all elements that matched the condition and its second property containing the elements that did not match.

Upvotes: 5

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