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• cats-laws_sjs0.6_2.11
• 0.3.0
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• ApplyLaws.scala

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cats.laws.ApplyLaws.scala Maven / Gradle / Ivy

package cats
package laws

import cats.syntax.apply._
import cats.syntax.functor._

/**
 * Laws that must be obeyed by any `Apply`.
 */
trait ApplyLaws[F[_]] extends FunctorLaws[F] {
  implicit override def F: Apply[F]

  def applyComposition[A, B, C](fa: F[A], fab: F[A => B], fbc: F[B => C]): IsEq[F[C]] = {
    val compose: (B => C) => (A => B) => (A => C) = _.compose
    fa.ap(fab).ap(fbc) <-> fa.ap(fab.ap(fbc.map(compose)))
  }
}

object ApplyLaws {
  def apply[F[_]](implicit ev: Apply[F]): ApplyLaws[F] =
    new ApplyLaws[F] { def F: Apply[F] = ev }
}