com.aol.cyclops

Interface Reducer<T>

Type Parameters:

T - Type this Reducer operates on

All Superinterfaces:

java.util.function.BiFunction<T,T,T>, java.util.function.BinaryOperator<T>, Monoid<T>, Semigroup<T>

public interface Reducer<T>
extends Monoid<T>

A class that extends Monoid to include a map operation to map to the type of the identity element first (to make reduction to immutable collections, for example, easier to work with in Java 8 Streams).

Method Summary

Modifier and Type	Method and Description
static <T> Reducer<T>	fromMonoid(Monoid<T> monoid, java.util.function.Function<?,? extends T> mapper)
default T	mapReduce(java.util.stream.Stream<?> toReduce) Map a given Stream to required type (via mapToType method), then reduce using this monoid Example of multiple reduction using multiple Monoids and PowerTuples
default java.util.stream.Stream<T>	mapToType(java.util.stream.Stream<?> stream) Map this reducer to the supported Type t.
static <T> Reducer<T>	of(T zero, java.util.function.BiFunction<T,T,T> combiner, java.util.function.Function<?,? extends T> mapToType)
static <T> Reducer<T>	of(T zero, java.util.function.Function<T,java.util.function.Function<T,T>> combiner, java.util.function.Function<?,T> mapToType)

Methods inherited from interface com.aol.cyclops.Monoid

fromBiFunction, of, of, reduce, zero

Methods inherited from interface com.aol.cyclops.Semigroup

apply, combiner, reducer

Methods inherited from interface java.util.function.BinaryOperator

maxBy, minBy

Methods inherited from interface java.util.function.BiFunction

andThen

Method Detail

mapToType

default java.util.stream.Stream<T> mapToType(java.util.stream.Stream<?> stream)

Map this reducer to the supported Type t. Default implementation is a simple cast.

Parameters:

stream - Stream to convert

Returns:

Converted Stream

mapReduce

default T mapReduce(java.util.stream.Stream<?> toReduce)

Map a given Stream to required type (via mapToType method), then reduce using this monoid Example of multiple reduction using multiple Monoids and PowerTuples

 
  Monoid<Integer> sum = Monoid.of(0,(a,b)->a+b);
	Monoid<Integer> mult = Monoid.of(1,(a,b)->a*b);
	<PTuple2<Integer,Integer>> result = PowerTuples.tuple(sum,mult).<PTuple2<Integer,Integer>>asReducer()
										.mapReduce(Stream.of(1,2,3,4)); 
	 
	assertThat(result,equalTo(tuple(10,24)));
  

Parameters:

toReduce - Stream to reduce

Returns:

reduced value

fromMonoid

static <T> Reducer<T> fromMonoid(Monoid<T> monoid,
                                 java.util.function.Function<?,? extends T> mapper)

of

static <T> Reducer<T> of(T zero,
                         java.util.function.BiFunction<T,T,T> combiner,
                         java.util.function.Function<?,? extends T> mapToType)

of

static <T> Reducer<T> of(T zero,
                         java.util.function.Function<T,java.util.function.Function<T,T>> combiner,
                         java.util.function.Function<?,T> mapToType)