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

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/*
 * Copyright (c) 2018-2022, 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.Kind;
import com.github.tonivade.purefun.monad.Reader;
import com.github.tonivade.purefun.monad.ReaderOf;
import com.github.tonivade.purefun.monad.Reader_;
import com.github.tonivade.purefun.typeclasses.Monad;
import com.github.tonivade.purefun.typeclasses.MonadReader;

@SuppressWarnings("unchecked")
public interface ReaderInstances {

  static  Monad> monad() {
    return ReaderMonad.INSTANCE;
  }

  static  MonadReader, R> monadReader() {
    return ReaderMonadReader.INSTANCE;
  }
}

interface ReaderMonad extends Monad> {

  @SuppressWarnings("rawtypes")
  ReaderMonad INSTANCE = new ReaderMonad() {};

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

  @Override
  default  Reader flatMap(Kind, ? extends T> value,
      Function1, ? extends V>> map) {
    return ReaderOf.narrowK(value).flatMap(map.andThen(ReaderOf::narrowK));
  }
}

interface ReaderMonadReader extends MonadReader, R>, ReaderMonad {

  @SuppressWarnings("rawtypes")
  ReaderMonadReader INSTANCE = new ReaderMonadReader() {};

  @Override
  default Kind, R> ask() {
    return Reader.env();
  }
}