Idiomatic way to create n-ary cartesian product (combinations of several sets of parameters)

Question

To create all possible combinations of two sets of parameters and perform an action on them, you can do:

setOf(foo, bar, baz).forEach { a ->
    setOf(0,          


        

Answer 1

I would recommend using Arrow-kt's Applicative on List. See the example:

val ints = listOf(1, 2, 3, 4)
val strings = listOf("a", "b", "c")
val booleans = listOf(true, false)

val combined = ListK.applicative()
    .tupled(ints.k(), strings.k(), booleans.k())
    .fix()

// or use the shortcut `arrow.instances.list.applicative.tupled`
// val combined = tupled(ints, strings, booleans)

combined.forEach { (a, b, c) -> println("a=$a, b=$b, c=$c") }

Which produces the Cartesian product

a=1, b=a, c=true

a=1, b=b, c=true

a=1, b=c, c=true

a=2, b=a, c=true

a=2, b=b, c=true

a=2, b=c, c=true

a=3, b=a, c=true

a=3, b=b, c=true

a=3, b=c, c=true

a=4, b=a, c=true

a=4, b=b, c=true

a=4, b=c, c=true

a=1, b=a, c=false

a=1, b=b, c=false

a=1, b=c, c=false

a=2, b=a, c=false

a=2, b=b, c=false

a=2, b=c, c=false

a=3, b=a, c=false

a=3, b=b, c=false

a=3, b=c, c=false

a=4, b=a, c=false

a=4, b=b, c=false

a=4, b=c, c=false