stonehorse.candy

Class Iterables

java.lang.Object

stonehorse.candy.Iterables

public class Iterables
extends Object

Functions of iterables creating lazy iterators. As they are lazy they can be composed without memory exhaustion. It's all functions which you easily create new ones of to extend the functionality.

Method Summary

Modifier and Type	Method and Description
static <T> Iterable<T>	concat(Iterable<T> a, Iterable<T> b) Iterable of lazy iterators concatenating iterators from a and b *
static <T> Iterable<T>	cycle(Iterable<T> in) Iterable of lazy infinite iterators elements of in.
static <T> Iterable<T>	drop(int num, Iterable<T> iterable) Iterable of lazy iterators but the num first elements of iterable
static <T> Iterable<T>	dropLast(int num, Iterable<T> iterable) Iterable of lazy iterators emitting all elements except last num elements
static <T> Iterable<T>	dropWhile(Predicate<? super T> predicate, Iterable<T> iterable) Iterable of lazy iterators emitting all elements but except the first matching predicate
static <T> Iterable<T>	filter(Predicate<? super T> f, Iterable<T> data) Iterable of lazy iterators filtering another Iterable using a predicate
static <T> T	first(Iterable<T> iterable) The first element of the next iterator of iterable or null
static <V,A> Iterable<A>	flatMap(Function<? super V,Iterable<A>> f, Iterable<? extends V> data) Iterable of lazy iterators which concatenate the result of applying map to every element in iterators of data.
static <A,V> A	fold(BiFunction<? super A,? super V,? extends A> f, A accumulator, Iterable<? extends V> elements) Combines elements of the first iterator into a single result by repeated application of a combining operation f where the initial result is accumulator *
static <A> List<A>	forceList(Iterable<A> iterable) A new list with elements found in the next iterator of iterable
static <A> Set<A>	forceSet(Iterable<A> iterable) A new set with elements found in the next iterator of iterable
static <T> Iterable<T>	iterable(Stream<T> stream) Iterable of stream
static <T> Iterable<T>	iterate(Function<? super T,? extends T> function, T initial) Iterable of lazy infinite iterators iterating over function with initial value.
static <T> T	last(Iterable<T> i) The last element of the next iterator of iterable or null
static <A> List<A>	list(Iterable<A> iterable) A list with elements found in the next iterator of iterable.
static <A,B,V> Iterable<V>	map(BiFunction<? super A,? super B,V> f, Iterable<? extends A> i1, Iterable<? extends B> i2) Iterable of lazy iterators applying a combining function to every element induced by two Iterables, until one of the iterators are empty.
static <A,V> Iterable<V>	map(Function<? super A,V> f, Iterable<A> data) Iterable of lazy iterators applying a function to all element induced by a Iterable
static <T> Iterable<T>	next(Iterable<T> iterable) Iterable of lazy iterators emitting all elements but first from iterable or null if empty
static <T> T	nth(int i, Iterable<T> iterable) The nth element of the next iterator of iterable or null
static <T> Iterable<Iterable<T>>	partition(int num, Iterable<T> iterable) Iterable of lazy iterators partitioning elements into num long iterables
static <T> Iterable<Iterable<T>>	partitionBy(Function<? super T,Object> function, Iterable<T> iterable) Iterable of lazy iterators partitioning elements by application to function *
static Iterable<Integer>	range() Iterable of lazy iterators iterating from 0 to Integer.MAX_VALUE
static Iterable<Integer>	range(int n) Iterable of lazy iterators iterating from 0 to n
static Iterable<Integer>	range(int from, int to) Iterable of lazy iterators iterating from from to to
static Iterable<Integer>	range(int from, int to, int step) Iterable of lazy iterators iterating from from to to in steps of step
static <T> T	reduce(BiFunction<? super T,? super T,? extends T> f, Iterable<? extends T> elements) Combines elements of the first iterator into a single result by repeated application of a combining operation f where the initial result is first element *
static <A,V> Iterable<V>	reductions(BiFunction<? super V,? super A,? extends V> f, V accumulator, Iterable<? extends A> elements) Iterable of lazy iterators producing intermediate values of the reduction of elements by f, starting with accumulator
static <T> Iterable<T>	repeat(int lim, T t)
static <T> Iterable<T>	repeat(T x) Iterable of lazy infinite iterators of x
static <T> Iterable<T>	repeatedly(Supplier<T> supplier) Iterable of lazy infinite iterators with invokes of supplier
static <T> Iterable<T>	rest(Iterable<T> iterable) Iterable of lazy iterators emitting all elements but first from iterable
static <T> T	second(Iterable<T> iterable) The second element of the next iterator of iterable or null
static <A> Set<A>	set(Iterable<A> iterable) A set with elements found in the next iterator of iterable.
static <T> Iterable<Iterable<T>>	splitAt(int i, Iterable<T> iterable) Tuple of Iterables of lazy iterators by spliting iterables iterators at i.
static <T> Iterable<Iterable<T>>	splitWith(Predicate<T> p, Iterable<T> iterable) Tuple of Iterables of lazy iterators by spliting iterables iterators by predicate.
static <T> Stream<T>	stream(Iterable<T> iterable) Stream of iterable
static <T> Iterable<T>	take(int num, Iterable<T> iterable) Iterable of lazy iterators having num first values of iterable
static <T> Iterable<T>	takeNth(int nth, Iterable<T> iterable) Iterable of lazy iterators with every nth element of iterables iterator
static <T> Iterable<T>	takeWhile(Predicate<? super T> pred, Iterable<T> iterable) Iterable of lazy iterators having the first elements matching predicate
static <T> Iterable<T>	with(T t, Iterable<? extends T> iterable) Iterable of lazy iterators prepending t to each iterator of iterable
static <T> Iterable<T>	withLast(Iterable<T> iterable, T b) Iterable of lazy iterators appending b to each iterator of iterable *

Methods inherited from class java.lang.Object

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

Method Detail

forceList

public static <A> List<A> forceList(Iterable<A> iterable)

A new list with elements found in the next iterator of iterable

list

public static <A> List<A> list(Iterable<A> iterable)

A list with elements found in the next iterator of iterable. The iterable itself if it happen to be a List

forceSet

public static <A> Set<A> forceSet(Iterable<A> iterable)

A new set with elements found in the next iterator of iterable

set

public static <A> Set<A> set(Iterable<A> iterable)

A set with elements found in the next iterator of iterable. The iterable itself if it happen to be a Set *

Example:

fold

public static <A,V> A fold(BiFunction<? super A,? super V,? extends A> f,
                           A accumulator,
                           Iterable<? extends V> elements)

Combines elements of the first iterator into a single result by repeated application of a combining operation f where the initial result is accumulator *

Example:

 fold((a,v)->a+v, 0, Arrays.asList(1,2,3,4)) => 10
 

reduce

public static <T> T reduce(BiFunction<? super T,? super T,? extends T> f,
                           Iterable<? extends T> elements)

Combines elements of the first iterator into a single result by repeated application of a combining operation f where the initial result is first element *

Example:

 fold((a,v)->a+v, 0, Arrays.asList(1,2,3,4)) => 10
 

filter

public static <T> Iterable<T> filter(Predicate<? super T> f,
                                     Iterable<T> data)

Iterable of lazy iterators filtering another Iterable using a predicate

Example:

 list(filter( e -> 0==e%2, Arrays.asList(1, 2, 3, 4))) => [2, 4]
 

map

public static <A,V> Iterable<V> map(Function<? super A,V> f,
                                    Iterable<A> data)

Iterable of lazy iterators applying a function to all element induced by a Iterable

Example:

 list(map( e -> e+1, Arrays.asList(1, 2, 3, 4))) => [2, 3, 4, 5]
 

map

public static <A,B,V> Iterable<V> map(BiFunction<? super A,? super B,V> f,
                                      Iterable<? extends A> i1,
                                      Iterable<? extends B> i2)

Iterable of lazy iterators applying a combining function to every element induced by two Iterables, until one of the iterators are empty.

Example:

 list(map( (a,b) -> a+b, Arrays.asList(1, 2, 3, 4), Arrays.asList(1, 2, 3))) => [2, 4, 6]
 

reductions

public static <A,V> Iterable<V> reductions(BiFunction<? super V,? super A,? extends V> f,
                                           V accumulator,
                                           Iterable<? extends A> elements)

Iterable of lazy iterators producing intermediate values of the reduction of elements by f, starting with accumulator

Example:

 list( reductions( (a,b) -> a+b, 0, Arrays.asList(1, 2, 3, 4))) => [1, 3, 6, 10]
 

drop

public static <T> Iterable<T> drop(int num,
                                   Iterable<T> iterable)

Iterable of lazy iterators but the num first elements of iterable

Example:

 list( drop( 2, Arrays.asList(1, 2, 3, 4))) => [3, 4]
 

first

public static <T> T first(Iterable<T> iterable)

The first element of the next iterator of iterable or null

Example:

 first(  Arrays.asList(1, 2, 3, 4)) => 1
 

second

public static <T> T second(Iterable<T> iterable)

The second element of the next iterator of iterable or null

Example:

 second( Arrays.asList(1, 2, 3, 4)) => 2
 

nth

public static <T> T nth(int i,
                        Iterable<T> iterable)

The nth element of the next iterator of iterable or null

Example:

 nth(2, Arrays.asList(1, 2, 3, 4)) => 3
 

take

public static <T> Iterable<T> take(int num,
                                   Iterable<T> iterable)

Iterable of lazy iterators having num first values of iterable

Example:

 list( take(2, Arrays.asList(1, 2, 3, 4))) => [1, 2]
 

takeWhile

public static <T> Iterable<T> takeWhile(Predicate<? super T> pred,
                                        Iterable<T> iterable)

Iterable of lazy iterators having the first elements matching predicate

Example:

 list( takeWhile(x -> x<3, Arrays.asList(1, 2, 3, 4))) => [1, 2]
 

last

public static <T> T last(Iterable<T> i)

The last element of the next iterator of iterable or null

Example:

 last(  Arrays.asList(1, 2, 3, 4)) => 4
 

takeNth

public static <T> Iterable<T> takeNth(int nth,
                                      Iterable<T> iterable)

Iterable of lazy iterators with every nth element of iterables iterator

Example:

 list( takeNth(2, Arrays.asList(1, 2, 3, 4))) => [1, 3]
 

flatMap

public static <V,A> Iterable<A> flatMap(Function<? super V,Iterable<A>> f,
                                        Iterable<? extends V> data)

Iterable of lazy iterators which concatenate the result of applying map to every element in iterators of data.

Example:

 list( flatMap((v) -> asList(v, v), asList(1, 2))) => [1, 1, 2, 2]
 

next

public static <T> Iterable<T> next(Iterable<T> iterable)

Iterable of lazy iterators emitting all elements but first from iterable or null if empty

Example:

 list( next( asList(1, 2, 3))) => [2, 2]
 list( next( asList(1))) => null
 

rest

public static <T> Iterable<T> rest(Iterable<T> iterable)

Iterable of lazy iterators emitting all elements but first from iterable

Example:

 list( rest( asList(1, 2, 3))) => [2, 2]
 list( rest( asList(1))) => []
 

dropLast

public static <T> Iterable<T> dropLast(int num,
                                       Iterable<T> iterable)

Iterable of lazy iterators emitting all elements except last num elements

Example:

 list( dropLast( 2, asList(1, 2, 3))) => [1]
 

dropWhile

public static <T> Iterable<T> dropWhile(Predicate<? super T> predicate,
                                        Iterable<T> iterable)

Iterable of lazy iterators emitting all elements but except the first matching predicate

Example:

 list( dropWhile( e -> e<3, asList(1, 2, 3))) => [3]
 

partition

public static <T> Iterable<Iterable<T>> partition(int num,
                                                  Iterable<T> iterable)

Iterable of lazy iterators partitioning elements into num long iterables

Example:

 list(map( Iterables::list,  list( partition( 3, asList(1, 2, 3, 4, 5, 6, 7))))) => [[1, 2, 3], [4, 5, 6]]
 

partitionBy

public static <T> Iterable<Iterable<T>> partitionBy(Function<? super T,Object> function,
                                                    Iterable<T> iterable)

Iterable of lazy iterators partitioning elements by application to function *

Example:

 list( map( Iterables::list,  partitionBy( v -> v%2, asList(1, 3, 4, 5, 7, 6)))) => [[1, 3], [4], [5, 7], [6]]
 

splitAt

public static <T> Iterable<Iterable<T>> splitAt(int i,
                                                Iterable<T> iterable)

Tuple of Iterables of lazy iterators by spliting iterables iterators at i. Two iterators of iterable will be created per iterator *

Example:

  list(map( Iterables::list, splitAt( 3, asList(1, 2, 3, 4, 5, 6, 7))))) => [[1, 2, 3], [4, 5, 6, 7]]
 

splitWith

public static <T> Iterable<Iterable<T>> splitWith(Predicate<T> p,
                                                  Iterable<T> iterable)

Tuple of Iterables of lazy iterators by spliting iterables iterators by predicate. Two iterators of iterable will be created per iterator. *

Example:

  list(map( Iterables::list, splitWith(v->v%2==0, asList(4,2,3,4)))) => [[4, 2], [3, 4]]
 

concat

public static <T> Iterable<T> concat(Iterable<T> a,
                                     Iterable<T> b)

Iterable of lazy iterators concatenating iterators from a and b *

Example:

  list(concat( asList(1,2), asList(3,4))) => [1, 2, 3, 4]
 

withLast

public static <T> Iterable<T> withLast(Iterable<T> iterable,
                                       T b)

Iterable of lazy iterators appending b to each iterator of iterable *

Example:

  list( withLast( asList(1,2), 3 )) => [1, 2, 3]
 

with

public static <T> Iterable<T> with(T t,
                                   Iterable<? extends T> iterable)

Iterable of lazy iterators prepending t to each iterator of iterable

Example:

  list( with( 1, asList(2,3))) => [1, 2, 3]
 

iterate

public static <T> Iterable<T> iterate(Function<? super T,? extends T> function,
                                      T initial)

Iterable of lazy infinite iterators iterating over function with initial value. That is initial, function(initial), function(function(initial)) and so on

Example:

  list(take(4, iterate(v -> v + 1, 5))) => [5, 6, 7, 8]
 

stream

public static <T> Stream<T> stream(Iterable<T> iterable)

Stream of iterable

iterable

public static <T> Iterable<T> iterable(Stream<T> stream)

Iterable of stream

repeatedly

public static <T> Iterable<T> repeatedly(Supplier<T> supplier)

Iterable of lazy infinite iterators with invokes of supplier

Example:

  list(take(3, repeatedly(() -> 4))) => [4, 4, 4]
 

repeat

public static <T> Iterable<T> repeat(T x)

Iterable of lazy infinite iterators of x

Example:

  list(take(3, repeat( 4))) => [4, 4, 4]
 

repeat

public static <T> Iterable<T> repeat(int lim,
                                     T t)

range

public static Iterable<Integer> range()

Iterable of lazy iterators iterating from 0 to Integer.MAX_VALUE

Example:

  list(take(3, range())) => [0, 1, 2]
 

range

public static Iterable<Integer> range(int n)

Iterable of lazy iterators iterating from 0 to n

Example:

  list(range(3)) => [0, 1, 2]
 

range

public static Iterable<Integer> range(int from,
                                      int to)

Iterable of lazy iterators iterating from from to to

Example:

  list(range(1,3)) => [1, 2]
 

range

public static Iterable<Integer> range(int from,
                                      int to,
                                      int step)

Iterable of lazy iterators iterating from from to to in steps of step

Example:

  list(range(1,5,3)) => [1, 4]
 

cycle

public static <T> Iterable<T> cycle(Iterable<T> in)

Iterable of lazy infinite iterators elements of in. A new iterator is created for each lap.

Example:

  list(take(5, cycle(asList(1,2,3)))) => [1, 2, 3, 1, 2]