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

Go to download
/*
 * 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.Producer;
import com.github.tonivade.purefun.type.Eval;
import com.github.tonivade.purefun.type.Eval.µ;
import com.github.tonivade.purefun.typeclasses.Applicative;
import com.github.tonivade.purefun.typeclasses.Comonad;
import com.github.tonivade.purefun.typeclasses.Defer;
import com.github.tonivade.purefun.typeclasses.Functor;
import com.github.tonivade.purefun.typeclasses.Monad;

public interface EvalInstances {

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

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

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

  static Comonad comonad() {
    return new EvalComonad() {};
  }

  static Defer defer() {
    return new EvalDefer() {};
  }
}

@Instance
interface EvalFunctor extends Functor {

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

@Instance
interface EvalPure extends Applicative {

  @Override
  default  Higher1<µ, T> pure(T value) {
    return Eval.now(value);
  }
}

@Instance
interface EvalApplicative extends EvalPure {

  @Override
  default  Higher1<µ, R> ap(Higher1<µ, T> value, Higher1<µ, Function1> apply) {
    return Eval.narrowK(value).flatMap(t -> Eval.narrowK(apply).map(f -> f.apply(t)));
  }
}

@Instance
interface EvalMonad extends EvalPure, Monad {

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

@Instance
interface EvalComonad extends EvalFunctor, Comonad {

  @Override
  default  Eval coflatMap(Higher1 value, Function1, B> map) {
    return Eval.later(() -> map.apply(value));
  }

  @Override
  default  A extract(Higher1 value) {
    return Eval.narrowK(value).value();
  }
}

@Instance
interface EvalDefer extends Defer {

  @Override
  default  Higher1<µ, A> defer(Producer> defer) {
    return Eval.defer(defer.andThen(Eval::narrowK));
  }
}