com.aol.cyclops.lambda.api

Interface Monoid<T>

Type Parameters:

T -

All Known Implementing Classes:

AsGenericMonoid.WrappedMonoid

public interface Monoid<T>

An interoperability trait for Monoids Also inteded for use with Java 8 Streams (reduce method) Practically the method signature to reduce matches the Monoid interface Monoids could regrarded as immutable equivalents to JDK Collectors for Immutable Reduction

Method Summary

Modifier and Type	Method and Description
java.util.function.BiFunction<T,T,T>	combiner()
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)));
default java.util.stream.Stream<T>	mapToType(java.util.stream.Stream stream)
static <T> Monoid<T>	of(T zero, java.util.function.BiFunction<T,T,T> combiner)
static <T> Monoid<T>	of(T zero, java.util.function.Function<T,java.util.function.Function<T,T>> combiner)
static <T> Monoid<T>	of(T zero, java.util.function.Function<T,java.util.function.Function<T,T>> combiner, java.util.function.Function<?,T> mapToType)
default T	reduce(java.util.stream.Stream<T> toReduce)
default java.util.function.BinaryOperator<T>	reducer()
T	zero() An element that when provided as a parameter to the combiner with another value, results in the other value being returned e.g.

Method Detail

zero

T zero()

An element that when provided as a parameter to the combiner with another value, results in the other value being returned e.g. 0 + 1 = 1 0 is zero() 1 * 2 = 2 1 is zero() "" + "hello" = "hello" "" is zero()

Returns:

combiner

java.util.function.BiFunction<T,T,T> combiner()

reducer

default java.util.function.BinaryOperator<T> reducer()

mapToType

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

reduce

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

of

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

of

static <T> Monoid<T> of(T zero,
                        java.util.function.Function<T,java.util.function.Function<T,T>> combiner)

of

static <T> Monoid<T> of(T zero,
                        java.util.function.BiFunction<T,T,T> combiner)