play.api.libs.functional.Applicative.scala Maven / Gradle / Ivy
/*
* Copyright (C) 2009-2018 Lightbend Inc.
*/
package play.api.libs.functional
import scala.language.higherKinds
trait Applicative[M[_]] {
def pure[A](a: A): M[A]
def map[A, B](m: M[A], f: A => B): M[B]
def apply[A, B](mf: M[A => B], ma: M[A]): M[B]
}
object Applicative {
implicit val applicativeOption: Applicative[Option] = new Applicative[Option] {
def pure[A](a: A): Option[A] = Some(a)
def map[A, B](m: Option[A], f: A => B): Option[B] = m.map(f)
def apply[A, B](mf: Option[A => B], ma: Option[A]): Option[B] = mf.flatMap(f => ma.map(f))
}
}
class ApplicativeOps[M[_], A](ma: M[A])(implicit a: Applicative[M]) {
def ~>[B](mb: M[B]): M[B] = a(a(a.pure((_: A) => (b: B) => b), ma), mb)
def andKeep[B](mb: M[B]): M[B] = ~>(mb)
def <~[B](mb: M[B]): M[A] = a(a(a.pure((a: A) => (_: B) => a), ma), mb)
def keepAnd[B](mb: M[B]): M[A] = <~(mb)
def <~>[B, C](mb: M[B])(implicit witness: <:<[A, B => C]): M[C] = apply(mb)
def apply[B, C](mb: M[B])(implicit witness: <:<[A, B => C]): M[C] = a(a.map(ma, witness), mb)
}