import arrow.core.NonEmptyList
import arrow.core.Validated

//sampleStart
fun <E, A, B, C> parallelValidate(v1: Validated<E, A>, v2: Validated<E, B>, f: (A, B) -> C): Validated<NonEmptyList<E>, C> =
  when {
    v1 is Validated.Valid && v2 is Validated.Valid -> Validated.Valid(f(v1.a, v2.a))
    v1 is Validated.Valid && v2 is Validated.Invalid -> v2.toValidatedNel()
    v1 is Validated.Invalid && v2 is Validated.Valid -> v1.toValidatedNel()
    v1 is Validated.Invalid && v2 is Validated.Invalid -> Validated.Invalid(NonEmptyList(v1.e, listOf(v2.e)))
    else -> throw IllegalStateException("Not possible value")
  }
//sampleEnd