Snoc

beginner

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.data.ListK
import arrow.optics.instances.listk.snoc.snoc
import arrow.optics.typeclasses.Snoc

val listLast = ListK.snoc<Int>().snoc()
val instance = Snoc(listLast)
instance

It defines two functions snoc and unsnoc.

snoc appends an element A to a structure S.

import arrow.optics.instances.list.snoc.snoc

listOf(1, 2).snoc(3)

unsnoc detaches the last element A from a structure S.

import arrow.optics.instances.list.snoc.unsnoc

listOf(1, 2, 3).unsnoc()
emptyList<Int>().unsnoc()

Data types

import arrow.reflect.*
import arrow.optics.typeclasses.*

TypeClass(Snoc::class).dtMarkdownList()