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scalacartesian-productscala-cats

Cartesian product of three lists with cats

Suppose I need to zip three lists to get a list of triplets. I can write it like that:

import cats._
import cats.data._
import cats.implicits._

(List(1, 2) |@| List(3, 4) |@| List(5, 6)) map {case (a, b, c) => (a, b, c)}
res1: List[(Int, Int, Int)] = List((1,3,5), (1,3,6), (1,4,5), (1,4,6), (2,3,5), (2,3,6), (2,4,5), (2,4,6))

Can you simplify it ?

Solution

  • With 1.1.0, it's simply (a, b, c).tupled. Ammonite script with all the imports and dependencies:

    @ import $ivy.`org.typelevel::cats-core:1.1.0`
@ import cats._, cats.data._, cats.implicits._

val triples = (List(1, 2), List(3, 4), List(5, 6)).tupled
println(triples)

    Output:

    List((1,3,5), (1,3,6), (1,4,5), (1,4,6), (2,3,5), (2,3,6), (2,4,5), (2,4,6))

    I wouldn't call it a "zip", however, it's rather a Cartesian product.