gololang

Class LazyList

java.lang.Object

gololang.LazyList

All Implemented Interfaces:

HeadTail<java.lang.Object>, java.lang.Iterable<java.lang.Object>, java.util.Collection<java.lang.Object>

public class LazyList
extends java.lang.Object
implements java.util.Collection<java.lang.Object>, HeadTail<java.lang.Object>

Represents a lazy list object.

A lazy list behaves like a linked list, but each next element is represented by a closure that is evaluated only if needed. The value is cached, so that the closure representing the tail is evaluated only once. Since the tail closure will be called at most once, and we can't guarantee when, or even if, it will be called, this closure must be a pure, side-effect free, function.

Field Summary

Fields

Modifier and Type	Field and Description
static LazyList	EMPTY Represents the empty list.

Method Summary

Modifier and Type	Method and Description
void	add(int index, java.lang.Object element)
boolean	add(java.lang.Object e)
boolean	addAll(java.util.Collection<?> c)
boolean	addAll(int index, java.util.Collection<?> c)
java.util.List<java.lang.Object>	asList() Convert the lazy list into a regular list.
void	clear()
static LazyList	cons(java.lang.Object head, FunctionReference tail) Create a new list from the head and tail values.
boolean	contains(java.lang.Object o) Check if the list contains the given object.
boolean	containsAll(java.util.Collection<?> c) Check if the list contains all the objects in the given collection.
Tuple	destruct() Destructuration helper.
boolean	equals(java.lang.Object o) Compares the specified object with this list.
java.lang.Object	get(int index) Returns the element at the specified position in this list.
int	hashCode() Compute the hashCode of this list.
java.lang.Object	head() Gets the first element of the list (its head).
int	indexOf(java.lang.Object o) Returns the position of the first occurrence of the given element in the list.
boolean	isEmpty() Checks whether the list is empty or not.
java.util.Iterator<java.lang.Object>	iterator() Creates an iterator over the list.
java.lang.Object	remove(int index)
boolean	remove(java.lang.Object e)
boolean	removeAll(java.util.Collection<?> c)
boolean	retainAll(java.util.Collection<?> c)
java.lang.Object	set(int index, java.lang.Object element)
int	size() Returns the number of elements in this list.
LazyList	tail() Gets the rest of the list (its tail).
java.lang.Object[]	toArray() Returns an array containing all of the elements in this list.
<T> T[]	toArray(T[] a) Returns an array containing all of the elements in this list with a type of the given array.
java.lang.String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Collection

parallelStream, removeIf, spliterator, stream

Methods inherited from interface gololang.HeadTail

toIterable

Methods inherited from interface java.lang.Iterable

forEach

Field Detail

EMPTY

public static final LazyList EMPTY

Represents the empty list.

Method Detail

cons

public static LazyList cons(java.lang.Object head,
                            FunctionReference tail)

Create a new list from the head and tail values.

Parameters:

head - the first value of the list.

tail - a FunctionReference that returns a LazyList when invoked.

Returns:

a new LazyList

head

public java.lang.Object head()

Gets the first element of the list (its head).

Specified by:

head in interface HeadTail<java.lang.Object>

Returns:

an Object, or null if the list is empty.

tail

public LazyList tail()

Gets the rest of the list (its tail).

Specified by:

tail in interface HeadTail<java.lang.Object>

Returns:

a LazyList, or EMPTY if the list is empty, contains only one value, or if the closure failed.

isEmpty

public boolean isEmpty()

Checks whether the list is empty or not.

Specified by:

isEmpty in interface HeadTail<java.lang.Object>

Specified by:

isEmpty in interface java.util.Collection<java.lang.Object>

Returns:

true if the list is EMPTY, false otherwise.

iterator

public java.util.Iterator<java.lang.Object> iterator()

Creates an iterator over the list.

The iterator does not support removal.

Specified by:

iterator in interface java.lang.Iterable<java.lang.Object>

Specified by:

iterator in interface java.util.Collection<java.lang.Object>

Returns:

an iterator.

asList

public java.util.List<java.lang.Object> asList()

Convert the lazy list into a regular list.

Note that it evaluates the whole list. Take care to not use this method on infinite lists, since no check is done.

Returns:

a new LinkedList

size

public int size()

Returns the number of elements in this list.

Note that it evaluates the whole list. Take care to not use this method on infinite lists, since no check is done.

Specified by:

size in interface java.util.Collection<java.lang.Object>

Returns:

the number of elements in this list.

equals

public boolean equals(java.lang.Object o)

Compares the specified object with this list.

This is a value comparison. Note that it may evaluate the whole list. Take care to not use this method on infinite lists, since no check is done.

Specified by:

equals in interface java.util.Collection<java.lang.Object>

Overrides:

equals in class java.lang.Object

Parameters:

o - the object to be compared for equality with this list

Returns:

true if the specified object is equal to this list.

hashCode

public int hashCode()

Compute the hashCode of this list.

Note that it evaluates the whole list. Take care to not use this method on infinite lists, since no check is done.

Specified by:

hashCode in interface java.util.Collection<java.lang.Object>

Overrides:

hashCode in class java.lang.Object

Returns:

the hashCode.

toArray

public java.lang.Object[] toArray()

Returns an array containing all of the elements in this list.

Note that it evaluates the whole list. Take care to not use this method on infinite lists, since no check is done.

Specified by:

toArray in interface java.util.Collection<java.lang.Object>

Returns:

an array containing all of the elements in this list

toArray

public <T> T[] toArray(T[] a)

Returns an array containing all of the elements in this list with a type of the given array.

Note that it evaluates the whole list. Take care to not use this method on infinite lists, since no check is done.

Specified by:

toArray in interface java.util.Collection<java.lang.Object>

Returns:

an array containing all of the elements in this list

destruct

public Tuple destruct()

Destructuration helper.

Returns:

a tuple of head and tail

get

public java.lang.Object get(int index)

Returns the element at the specified position in this list.

Note that it evaluates the list up to the required element.

Parameters:

index - index of the element to return

Returns:

the element at the specified position in this list

indexOf

public int indexOf(java.lang.Object o)

Returns the position of the first occurrence of the given element in the list.

Note that it evaluates the list up to the given element. Take care to not use this method on infinite lists, since no check is done.

Parameters:

o - element to search for

Returns:

the index of the first occurrence, or -1 if not present

contains

public boolean contains(java.lang.Object o)

Check if the list contains the given object.

Note that it evaluates the list up to the given element. Take care to not use this method on infinite lists, since no check is done.

Specified by:

contains in interface java.util.Collection<java.lang.Object>

Parameters:

o - element to search for

Returns:

true if the element is in the list, false otherwise.

containsAll

public boolean containsAll(java.util.Collection<?> c)

Check if the list contains all the objects in the given collection.

Note that it evaluates the list up to the given element, *for each* element in the collection (at worse). This implementation is highly inefficient.

Take care to not use this method on infinite lists, since no check is done.

Specified by:

containsAll in interface java.util.Collection<java.lang.Object>

Parameters:

c - collection of elements to search for

Returns:

true if all the elements are in the list, false otherwise.

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

add

public boolean add(java.lang.Object e)

Specified by:

add in interface java.util.Collection<java.lang.Object>

add

public void add(int index,
                java.lang.Object element)

addAll

public boolean addAll(java.util.Collection<?> c)

Specified by:

addAll in interface java.util.Collection<java.lang.Object>

addAll

public boolean addAll(int index,
                      java.util.Collection<?> c)

remove

public boolean remove(java.lang.Object e)

Specified by:

remove in interface java.util.Collection<java.lang.Object>

remove

public java.lang.Object remove(int index)

removeAll

public boolean removeAll(java.util.Collection<?> c)

Specified by:

removeAll in interface java.util.Collection<java.lang.Object>

retainAll

public boolean retainAll(java.util.Collection<?> c)

Specified by:

retainAll in interface java.util.Collection<java.lang.Object>

clear

public void clear()

Specified by:

clear in interface java.util.Collection<java.lang.Object>

set

public java.lang.Object set(int index,
                            java.lang.Object element)