scalaprops.ScalapropsShapeless.scala Maven / Gradle / Ivy
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package scalaprops
import shapeless3.deriving.K0
import scala.deriving.Mirror
sealed abstract class ScalapropsShapelessInstances {
final def cogenFromPolyFunction[A](f: [t] => (a: A, s: CogenState[t]) => CogenState[t]): Cogen[A] =
new Cogen[A] {
override def cogen[B](a: A, s: CogenState[B]) = f[B](a, s)
}
inline implicit def cogenCoproduct[A](using inst: => K0.CoproductInstances[Cogen, A]): Cogen[A] =
cogenFromPolyFunction[A](
[B] => (a: A, s: CogenState[B]) => inst.fold(a)([t <: A] => (c: Cogen[t], t: t) => c.cogen(t, s))
)
inline implicit def cogenProduct[A](using inst: => K0.ProductInstances[Cogen, A]): Cogen[A] =
cogenFromPolyFunction[A](
[B] =>
(a: A, s: CogenState[B]) =>
inst.foldLeft[CogenState[B]](a)(s)(
[t] => (acc: CogenState[B], c: Cogen[t], t: t) => c.cogen(t, acc)
)
)
inline implicit def genProduct[A](using inst: => K0.ProductInstances[Gen, A]): Gen[A] =
Gen.gen[A] { (size, rand) =>
val (x, y) = inst.unfold[Rand](rand) {
[t] =>
(r: Rand, g: Gen[t]) => {
val (next, a) = g.f(size, r)
(next, Option(a))
}
}
(x, y.get)
}
inline implicit def genCoproduct[A](using inst: => K0.CoproductInstances[Gen, A], mirror: Mirror.SumOf[A]): Gen[A] =
Gen.gen[A] { (size, r1) =>
val (r2, i) = r1.nextInt
val index = if (i == Int.MinValue) {
0
} else {
i.abs % valueOf[Tuple.Size[mirror.MirroredElemTypes]]
}
inst.inject[(Rand, A)](index) {
[t <: A] => (g: Gen[t]) => g.f(size, r2)
}
}
}
object ScalapropsShapeless extends ScalapropsShapelessInstances {
inline implicit def deriveGen[A](using gen: K0.Generic[A]): Gen[A] =
gen.derive(genProduct, genCoproduct)
inline implicit def deriveCogen[A](using gen: K0.Generic[A]): Cogen[A] =
gen.derive(cogenProduct, cogenCoproduct)
}