Snoc

Snoc provides a Prism between S and its init A and last element S. Snoc can be seen as the reverse of Cons; it provides a way to attach or detach elements on the end side of a structure.

It can be constructed by providing the Prism.

import arrow.core.ListK
import arrow.optics.extensions.listk.snoc.snoc
import arrow.optics.typeclasses.Snoc

val listLast = ListK.snoc<Int>().snoc()
val instance = Snoc(listLast)
instance
// arrow.optics.typeclasses.Snoc$Companion$invoke$1@69c06bdc

It defines two functions snoc and unsnoc.

snoc appends an element A to a structure S.

import arrow.optics.extensions.list.snoc.snoc

listOf(1, 2).snoc(3)
// [1, 2, 3]

unsnoc detaches the last element A from a structure S.

import arrow.optics.extensions.list.snoc.unsnoc

listOf(1, 2, 3).unsnoc()
// Some(([1, 2], 3))
emptyList<Int>().unsnoc()
// None

Data types

Module Data types
arrow.core ListK

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