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• MaybeInstances.java

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cyclops.instances.control.MaybeInstances Maven / Gradle / Ivy

package cyclops.instances.control;

import com.oath.cyclops.hkt.DataWitness;
import com.oath.cyclops.hkt.DataWitness.option;
import com.oath.cyclops.hkt.Higher;
import cyclops.arrow.Cokleisli;
import cyclops.arrow.Kleisli;
import cyclops.arrow.MonoidK;
import cyclops.arrow.MonoidKs;
import cyclops.control.Either;
import cyclops.control.Maybe;
import cyclops.control.Option;
import cyclops.data.tuple.Tuple2;
import cyclops.function.Monoid;
import cyclops.hkt.Active;
import cyclops.hkt.Coproduct;
import cyclops.hkt.Nested;
import cyclops.hkt.Product;
import cyclops.kinds.OptionalKind;
import cyclops.typeclasses.InstanceDefinitions;
import cyclops.typeclasses.Pure;
import cyclops.typeclasses.comonad.Comonad;
import cyclops.typeclasses.foldable.Foldable;
import cyclops.typeclasses.foldable.Unfoldable;
import cyclops.typeclasses.functor.Functor;
import cyclops.typeclasses.monad.Applicative;
import cyclops.typeclasses.monad.Monad;
import cyclops.typeclasses.monad.MonadPlus;
import cyclops.typeclasses.monad.MonadRec;
import cyclops.typeclasses.monad.MonadZero;
import cyclops.typeclasses.monad.Traverse;
import cyclops.typeclasses.monad.TraverseByTraverse;
import lombok.AllArgsConstructor;
import lombok.experimental.UtilityClass;

import java.util.function.Function;

/**
 * Companion class for creating Type Class instances for working with Maybes
 * @author johnmcclean
 *
 */
@UtilityClass
public class MaybeInstances {
  public static  Maybe fromOptionalKind(final OptionalKind opt){
    return fromOptional(OptionalKind.narrow(opt));
  }
  public static   Kleisli,T> kindKleisli(){
    return Kleisli.of(MaybeInstances.monad(), Maybe::widen);
  }

  public static  Cokleisli> kindCokleisli(){
    return Cokleisli.of(Maybe::narrowK);
  }
  public static  Nested nested(Maybe> nested, InstanceDefinitions def2){

    return Nested.of(nested, MaybeInstances.definitions(),def2);
  }
  public static  Product product(Maybe m, Active active){
    return Product.of(allTypeclasses(m),active);
  }
  public static  Coproduct coproduct(Maybe m, InstanceDefinitions def2){
    return Coproduct.right(m,def2, MaybeInstances.definitions());
  }
  public static  Active allTypeclasses(Maybe m){
    return Active.of(m, MaybeInstances.definitions());
  }
  public static  Nested mapM(Maybe m,Function> fn, InstanceDefinitions defs){
    return Nested.of(m.map(fn), MaybeInstances.definitions(), defs);
  }


  /**
   * Construct an equivalent Maybe from the Supplied Optional
   * 
   * {@code
   *   MaybeType some = MaybeType.fromOptional(Optional.of(10));
   *   //Maybe[10], Some[10]
   *
   *   MaybeType none = MaybeType.fromOptional(Optional.zero());
   *   //Maybe.zero, None[]
   * }
   * 
   *
   * @param optional Optional to construct Maybe from
   * @return Maybe created from Optional
   */
  public static  Maybe fromOptional(Higher optional){
    return   Maybe.fromOptional(OptionalKind.narrowK(optional));

  }

  public static InstanceDefinitions definitions(){
    return new InstanceDefinitions() {
      @Override
      public  Functor functor() {
        return MaybeInstances.functor();
      }

      @Override
      public  Pure unit() {
        return MaybeInstances.unit();
      }

      @Override
      public  Applicative applicative() {
        return MaybeInstances.applicative();
      }

      @Override
      public  Monad monad() {
        return MaybeInstances.monad();
      }

      @Override
      public  Option> monadZero() {
        return Option.some(MaybeInstances.monadZero());
      }

      @Override
      public  Option> monadPlus() {
        return Option.some(MaybeInstances.monadPlus());
      }

      @Override
      public  MonadRec monadRec() {
        return MaybeInstances.monadRec();
      }

      @Override
      public  Option> monadPlus(MonoidK m) {
        return Option.some(MaybeInstances.monadPlus(m));
      }

      @Override
      public  Traverse traverse() {
        return MaybeInstances.traverse();
      }


      @Override
      public  Foldable foldable() {
        return MaybeInstances.foldable();
      }

      @Override
      public  Option> comonad() {
        return Maybe.nothing();
      }

      @Override
      public  Option> unfoldable() {
        return Maybe.nothing();
      }
    };
  }

    private final OptionInstances.OptionTypeclasses INSTANCE = new OptionInstances.OptionTypeclasses();

    @AllArgsConstructor
    public static class OptionTypeclasses  implements MonadPlus,
                                                        MonadRec,
                                                        TraverseByTraverse,
                                                        Foldable,
                                                        Unfoldable{

        @Override
        public  T foldRight(Monoid monoid, Higher ds) {
            return Maybe.narrowK(ds).fold(monoid);
        }



        @Override
        public  T foldLeft(Monoid monoid, Higher ds) {
            return Maybe.narrowK(ds).fold(monoid);
        }

        @Override
        public  Higher unfold(T b, Function>> fn) {
            return Maybe.fromPublisher(fn.apply(b).map(t->t._1()));
        }

        @Override
        public  MonoidK monoid() {
            return MonoidKs.firstPresentMaybe();
        }

        @Override
        public  Higher flatMap(Function> fn, Higher ds) {
            return Maybe.narrowK(ds).flatMap(t-> Option.narrowK(fn.apply(t)));
        }

        @Override
        public  Higher> traverseA(Applicative applicative, Function> fn, Higher ds) {
            Maybe maybe = Maybe.narrowK(ds);
            return maybe.fold(some-> applicative.map(m->Option.of(m), fn.apply(some)),
                ()->applicative.unit(Option.none()));
        }

        @Override
        public  R foldMap(Monoid mb, Function fn, Higher ds) {
            Maybe  opt  = Maybe.narrowK(ds).map(fn);
            return opt.fold(mb);
        }

        @Override
        public  Higher ap(Higher> fn, Higher apply) {
            return Maybe.narrowK(apply).zip(Option.narrowK(fn), (a, b)->b.apply(a));
        }

        @Override
        public  Higher unit(T value) {
            return Maybe.just(value);
        }

        @Override
        public  Higher map(Function fn, Higher ds) {
            return Maybe.narrowK(ds).map(fn);
        }

        @Override
        public  Higher tailRec(T initial, Function>> fn) {
            return Maybe.tailRec(initial,t-> Maybe.narrowK(fn.apply(t)));
        }
    }
    public static Functor functor(){
        return INSTANCE;
    }

    public static  Pure unit(){
        return INSTANCE;
    }

    public static  Applicative applicative(){
        return INSTANCE;
    }

    public static  Monad monad(){
        return INSTANCE;
    }
    public static  MonadRec monadRec(){

        return INSTANCE;
    }

    public static  MonadZero monadZero(){

        return INSTANCE;
    }

    public static  MonadPlus monadPlus(){
        return INSTANCE;
    }

    public static  MonadPlus monadPlus(MonoidK m){

        return INSTANCE;
    }


    public static  Traverse traverse(){
        return INSTANCE;
    }


    public static  Foldable foldable(){
        return INSTANCE;
    }




}