cron4s.base.Predicate.scala Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of cron4s-core_sjs0.6_2.12 Show documentation

CRON expression parser for Scala

There is a newer version: 0.6.1

Show newest version

/*
 * Copyright 2017 Antonio Alonso Dominguez
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package cron4s.base

import cats.{Monoid, MonoidK}
import cats.Contravariant

import cron4s.syntax.predicate._

/**
  * Created by alonsodomin on 02/01/2016.
  */
trait Predicate[A] extends (A => Boolean) { self =>

  def apply(a: A): Boolean

  def and(m: => Predicate[A]): Predicate[A] = Predicate { a => self(a) && m(a) }
  def or(m: => Predicate[A]): Predicate[A] = Predicate { a => self(a) || m(a) }

  def &&(m: => Predicate[A]): Predicate[A] = and(m)
  def ||(m: => Predicate[A]): Predicate[A] = or(m)

  def unary_! : Predicate[A] = not(self)

}

object Predicate {

  def apply[A](f: A => Boolean): Predicate[A] = new Predicate[A] {
    def apply(a: A): Boolean = f(a)
  }

  implicit val contravariant = new Contravariant[Predicate] {

    def contramap[A, B](fa: Predicate[A])(f: B => A): Predicate[B] =
      Predicate { b => fa(f(b)) }

  }

  object conjunction {
    implicit val monoidK: MonoidK[Predicate] = new MonoidK[Predicate] {
      def empty[A]: Predicate[A] = always(true)

      def combineK[A](x: Predicate[A], y: Predicate[A]): Predicate[A] = x && y
    }

    implicit def monoid[A]: Monoid[Predicate[A]] = monoidK.algebra[A]
  }

  object disjunction {
    implicit val monoidK: MonoidK[Predicate] = new MonoidK[Predicate] {
      def empty[A]: Predicate[A] = always(false)

      def combineK[A](x: Predicate[A], y: Predicate[A]): Predicate[A] = x || y
    }

    implicit def monoid[A]: Monoid[Predicate[A]] = monoidK.algebra[A]
  }

}