com.aol.cyclops.hkt.instances.jdk

Class ListInstances

java.lang.Object

com.aol.cyclops.hkt.instances.jdk.ListInstances

public class ListInstances
extends java.lang.Object

Companion class for creating Type Class instances for working with Lists

Constructor Summary

Constructors

Constructor and Description
ListInstances()

Method Summary

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

ListInstances

public ListInstances()

Method Detail

main

public static void main(java.lang.String[] args)

functor

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

Transform a list, mulitplying every element by 2

  
  ListType<Integer> list = Lists.functor().map(i->i*2, ListType.widen(Arrays.asList(1,2,3));
  
  //[2,4,6]
  
 
 
 

An example fluent api working with Lists

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

Returns:

A functor for Lists

unit

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

  
 ListType<String> list = Lists.unit()
                                     .unit("hello")
                                     .convert(ListType::narrowK);
        
        //Arrays.asList("hello"))
 
 
 

Returns:

A factory for Lists

zippingApplicative

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

  
 import static com.aol.cyclops.hkt.jdk.ListType.widen;
 import static com.aol.cyclops.util.function.Lambda.l1;
 import static java.util.Arrays.asList;
 
       Lists.zippingApplicative()
            .ap(widen(asList(l1(this::multiplyByTwo))),widen(asList(1,2,3)));
 
 //[2,4,6]
 
 

Example fluent API

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

Returns:

A zipper for Lists

monad

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

  
 import static com.aol.cyclops.hkt.jdk.ListType.widen;
 ListType<Integer> list  = Lists.monad()
                                      .flatMap(i->widen(ListX.range(0,i)), widen(Arrays.asList(1,2,3)))
                                      .convert(ListType::narrowK);
 
 

Example fluent API

  
    ListType<Integer> list = Lists.unit()
                                        .unit("hello")
                                        .then(h->Lists.monad().flatMap((String v) ->Lists.unit().unit(v.length()), h))
                                        .convert(ListType::narrowK);
        
        //Arrays.asList("hello".length())
 
 
 

Returns:

Type class with monad functions for Lists

monadZero

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

  
  ListType<String> list = Lists.unit()
                                     .unit("hello")
                                     .then(h->Lists.monadZero().filter((String t)->t.startsWith("he"), h))
                                     .convert(ListType::narrowK);
        
       //Arrays.asList("hello"));
 
 
 

Returns:

A filterable monad (with default value)

monadPlus

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

  
  ListType<Integer> list = Lists.<Integer>monadPlus()
                                      .plus(ListType.widen(Arrays.asList()), ListType.widen(Arrays.asList(10)))
                                      .convert(ListType::narrowK);
        //Arrays.asList(10))
 
 
 

Returns:

Type class for combining Lists by concatenation

monadPlus

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

  
  Monoid<ListType<Integer>> m = Monoid.of(ListType.widen(Arrays.asList()), (a,b)->a.isEmpty() ? b : a);
        ListType<Integer> list = Lists.<Integer>monadPlus(m)
                                      .plus(ListType.widen(Arrays.asList(5)), ListType.widen(Arrays.asList(10)))
                                      .convert(ListType::narrowK);
        //Arrays.asList(5))
 
 
 

Parameters:

m - Monoid to use for combining Lists

Returns:

Type class for combining Lists

traverse

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

Returns:

Type class for traversables with traverse / sequence operations

foldable

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

  
 int sum  = Lists.foldable()
                        .foldLeft(0, (a,b)->a+b, ListType.widen(Arrays.asList(1,2,3,4)));
        
        //10
 
 
 

Returns:

Type class for folding / reduction operations