Divide

Divide is a typeclass that models the divide part of divide and conquer. Divide basically states: Given a Kind<F, A> and a Kind<F, B>, and a way to turn C into a tuple of A and B, it provides you a Kind<F, C>.

A useful example is deriving serializers for a datatype from simpler serializers.

Here, we can easily construct a serializer for a Tuple<A, B> because we already have a serializer for A and B. Since most data classes can be expressed with tuples, writing serializers by combining them like this is trivial.

import arrow.typeclasses.Divide
import arrow.Kind
import arrow.core.Tuple2
import arrow.core.toT
import com.example.domain.*

data class User(val name: String, val age: Int)

val stringSerializer = Serializer<String> { "STRING: $it" }
val intSerializer = Serializer<Int> { "INT: $it" }

fun main(args: Array<String>) {
  //sampleStart
   val userSerializer: Serializer<User> = Serializer.divide().divide(
     stringSerializer,
     intSerializer
  ) { user: User ->
     user.name toT user.age
  }.fix()

  val user = User("John", 31)

  val result = userSerializer.func(user)
  //sampleEnd
  println(result)
}

Main Combinators

divide

Derive a value of Kind<F, C> from a Kind<F, A>, a Kind<F, B> and a function (C) -> Tuple2<A, B>.

Laws

Arrow provides DivideLaws in the form of test cases for internal verification of lawful instances and third party apps creating their own Divide instances.

See Deriving and creating custom typeclass to provide your own Divide instances for custom datatypes.