com.aol.cyclops.hkt.instances.jdk

Class StreamInstances

java.lang.Object

com.aol.cyclops.hkt.instances.jdk.StreamInstances

public class StreamInstances
extends java.lang.Object

Companion class for creating Type Class instances for working with Streams

Constructor Summary

Constructors

Constructor and Description
StreamInstances()

Method Summary

Modifier and Type	Method and Description
static <T> Foldable<com.aol.cyclops.hkt.jdk.StreamType.µ>	foldable() int sum = Streams.foldable() .foldLeft(0, (a,b)->a+b, StreamType.widen(Stream.of(1,2,3,4))); //10
static <T,R> Functor<com.aol.cyclops.hkt.jdk.StreamType.µ>	functor() Transform a list, mulitplying every element by 2
static <T,R> Monad<com.aol.cyclops.hkt.jdk.StreamType.µ>	monad() import static com.aol.cyclops.hkt.jdk.StreamType.widen; StreamType<Integer> list = Streams.monad() .flatMap(i->widen(StreamX.range(0,i)), widen(Stream.of(1,2,3))) .convert(StreamType::narrowK);
static <T> MonadPlus<com.aol.cyclops.hkt.jdk.StreamType.µ>	monadPlus() StreamType<Integer> list = Streams.<Integer>monadPlus() .plus(StreamType.widen(Stream.of()), StreamType.widen(Stream.of(10))) .convert(StreamType::narrowK); //Stream.of(10))
static <T> MonadPlus<com.aol.cyclops.hkt.jdk.StreamType.µ>	monadPlus(com.aol.cyclops.Monoid<com.aol.cyclops.hkt.jdk.StreamType<T>> m) Monoid<StreamType<Integer>> m = Monoid.of(StreamType.widen(Stream.of()), (a,b)->a.isEmpty() ? b : a); StreamType<Integer> list = Streams.<Integer>monadPlus(m) .plus(StreamType.widen(Stream.of(5)), StreamType.widen(Stream.of(10))) .convert(StreamType::narrowK); //Stream.of(5))
static <T,R> MonadZero<com.aol.cyclops.hkt.jdk.StreamType.µ>	monadZero() StreamType<String> list = Streams.unit() .unit("hello") .then(h->Streams.monadZero().filter((String t)->t.startsWith("he"), h)) .convert(StreamType::narrowK); //Stream.of("hello"));
static <C2,T> Traverse<com.aol.cyclops.hkt.jdk.StreamType.µ>	traverse()
static <T> Unit<com.aol.cyclops.hkt.jdk.StreamType.µ>	unit() StreamType<String> list = Streams.unit() .unit("hello") .convert(StreamType::narrowK); //Stream.of("hello"))
static <T,R> Applicative<com.aol.cyclops.hkt.jdk.StreamType.µ>	zippingApplicative() import static com.aol.cyclops.hkt.jdk.StreamType.widen; import static com.aol.cyclops.util.function.Lambda.l1; Streams.zippingApplicative() .ap(widen(Stream.of(l1(this::multiplyByTwo))),widen(Stream.of(1,2,3))); //[2,4,6]

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

StreamInstances

public StreamInstances()

Method Detail

functor

public static <T,R> Functor<com.aol.cyclops.hkt.jdk.StreamType.µ> functor()

Transform a list, mulitplying every element by 2

  
  StreamType<Integer> list = Streams.functor().map(i->i*2, StreamType.widen(Stream.of(1,2,3));
  
  //[2,4,6]
  
 
 
 

An example fluent api working with Streams

  
   StreamType<Integer> list = Streams.unit()
                                       .unit("hello")
                                       .then(h->Streams.functor().map((String v) ->v.length(), h))
                                       .convert(StreamType::narrowK);
 
 
 

Returns:

A functor for Streams

unit

public static <T> Unit<com.aol.cyclops.hkt.jdk.StreamType.µ> unit()

  
 StreamType<String> list = Streams.unit()
                                     .unit("hello")
                                     .convert(StreamType::narrowK);
        
        //Stream.of("hello"))
 
 
 

Returns:

A factory for Streams

zippingApplicative

public static <T,R> Applicative<com.aol.cyclops.hkt.jdk.StreamType.µ> zippingApplicative()

  
 import static com.aol.cyclops.hkt.jdk.StreamType.widen;
 import static com.aol.cyclops.util.function.Lambda.l1;
 
       Streams.zippingApplicative()
            .ap(widen(Stream.of(l1(this::multiplyByTwo))),widen(Stream.of(1,2,3)));
 
 //[2,4,6]
 
 

Example fluent API

  
 StreamType<Function<Integer,Integer>> listFn =Streams.unit()
                                                  .unit(Lambda.l1((Integer i) ->i*2))
                                                  .convert(StreamType::narrowK);
        
        StreamType<Integer> list = Streams.unit()
                                      .unit("hello")
                                      .then(h->Streams.functor().map((String v) ->v.length(), h))
                                      .then(h->Streams.zippingApplicative().ap(listFn, h))
                                      .convert(StreamType::narrowK);
        
        //Stream.of("hello".length()*2))
 
 
 

Returns:

A zipper for Streams

monad

public static <T,R> Monad<com.aol.cyclops.hkt.jdk.StreamType.µ> monad()

  
 import static com.aol.cyclops.hkt.jdk.StreamType.widen;
 StreamType<Integer> list  = Streams.monad()
                                      .flatMap(i->widen(StreamX.range(0,i)), widen(Stream.of(1,2,3)))
                                      .convert(StreamType::narrowK);
 
 

Example fluent API

  
    StreamType<Integer> list = Streams.unit()
                                        .unit("hello")
                                        .then(h->Streams.monad().flatMap((String v) ->Streams.unit().unit(v.length()), h))
                                        .convert(StreamType::narrowK);
        
        //Stream.of("hello".length())
 
 
 

Returns:

Type class with monad functions for Streams

monadZero

public static <T,R> MonadZero<com.aol.cyclops.hkt.jdk.StreamType.µ> monadZero()

  
  StreamType<String> list = Streams.unit()
                                         .unit("hello")
                                         .then(h->Streams.monadZero().filter((String t)->t.startsWith("he"), h))
                                         .convert(StreamType::narrowK);
        
       //Stream.of("hello"));
 
 
 

Returns:

A filterable monad (with default value)

monadPlus

public static <T> MonadPlus<com.aol.cyclops.hkt.jdk.StreamType.µ> monadPlus()

  
  StreamType<Integer> list = Streams.<Integer>monadPlus()
                                      .plus(StreamType.widen(Stream.of()), StreamType.widen(Stream.of(10)))
                                      .convert(StreamType::narrowK);
        //Stream.of(10))
 
 
 

Returns:

Type class for combining Streams by concatenation

monadPlus

public static <T> MonadPlus<com.aol.cyclops.hkt.jdk.StreamType.µ> monadPlus(com.aol.cyclops.Monoid<com.aol.cyclops.hkt.jdk.StreamType<T>> m)

  
  Monoid<StreamType<Integer>> m = Monoid.of(StreamType.widen(Stream.of()), (a,b)->a.isEmpty() ? b : a);
        StreamType<Integer> list = Streams.<Integer>monadPlus(m)
                                      .plus(StreamType.widen(Stream.of(5)), StreamType.widen(Stream.of(10)))
                                      .convert(StreamType::narrowK);
        //Stream.of(5))
 
 
 

Parameters:

m - Monoid to use for combining Streams

Returns:

Type class for combining Streams

traverse

public static <C2,T> Traverse<com.aol.cyclops.hkt.jdk.StreamType.µ> traverse()

Returns:

Type class for traversables with traverse / sequence operations

foldable

public static <T> Foldable<com.aol.cyclops.hkt.jdk.StreamType.µ> foldable()

  
 int sum  = Streams.foldable()
                        .foldLeft(0, (a,b)->a+b, StreamType.widen(Stream.of(1,2,3,4)));
        
        //10
 
 
 

Returns:

Type class for folding / reduction operations