com.github.tonivade.purefun.instances.TrampolineInstances Maven / Gradle / Ivy

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/*
 * Copyright (c) 2018-2019, Antonio Gabriel Muñoz Conejo 
 * Distributed under the terms of the MIT License
 */
package com.github.tonivade.purefun.instances;

import com.github.tonivade.purefun.Function1;
import com.github.tonivade.purefun.Higher1;
import com.github.tonivade.purefun.Instance;
import com.github.tonivade.purefun.monad.Trampoline;
import com.github.tonivade.purefun.typeclasses.Applicative;
import com.github.tonivade.purefun.typeclasses.Functor;
import com.github.tonivade.purefun.typeclasses.Monad;

public interface TrampolineInstances {

  static Functor functor() {
    return new TrampolineFunctor() {};
  }

  static Applicative applicative() {
    return new TrampolineApplicative() {};
  }

  static Monad monad() {
    return new TrampolineMonad() {};
  }
}

@Instance
interface TrampolineFunctor extends Functor {

  @Override
  default  Trampoline map(Higher1 value, Function1 mapper) {
    return Trampoline.narrowK(value).map(mapper);
  }
}

@Instance
interface TrampolinePure extends Applicative {

  @Override
  default  Trampoline pure(T value) {
    return Trampoline.done(value);
  }
}

@Instance
interface TrampolineApplicative extends TrampolinePure {

  @Override
  default  Trampoline ap(Higher1 value, Higher1> apply) {
    return Trampoline.narrowK(value).flatMap(t -> Trampoline.narrowK(apply).map(f -> f.apply(t)));
  }
}

@Instance
interface TrampolineMonad extends TrampolinePure, Monad {

  @Override
  default  Trampoline flatMap(Higher1 value,
      Function1> map) {
    return Trampoline.narrowK(value).flatMap(map.andThen(Trampoline::narrowK));
  }
}