lyng/docs/List.md

List built-in class

Mutable list of any objects.

It's class in Lyng is List:

[1,2,3]::class
>>> List

you can use it's class to ensure type:

[]::class == List
>>> true

Indexing

indexing is zero-based, as in C/C++/Java/Kotlin, etc.

val list = [10, 20, 30]
list[1]
>>> 20

There is a shortcut for the last:

val list = [10, 20, 30]
[list.last, list.lastIndex]
>>> [30,2]

Important negative indexes works wherever indexes are used, e.g. in insertion and removal methods too.

Concatenation

You can concatenate lists or iterable objects:

assert( [4,5] + [1,2] == [4,5,1,2])
assert( [4,5] + (1..3) == [4, 5, 1, 2, 3])
>>> void

Appending

To append to lists, use += with elements, lists and any Iterable instances, but beware it will concatenate Iterable objects instead of appending them. To append Iterable instance itself, use list.add:

var list = [1, 2]
val other = [3, 4]

// appending lists is clear:
list += other
assert( list == [1, 2, 3, 4] )

// but appending other Iterables could be confusing:
list += (10..12)
assert( list == [1, 2, 3, 4, 10, 11, 12])

// now adding list as sublist:
list.add(other)
assert( list == [1, 2, 3, 4, 10, 11, 12, [3,4]])

>>> void

Removing elements

List is mutable, so it is possible to remove its contents. To remove a single element by index use:

assertEquals( [1,2,3].removeAt(1), [1,3] )
assertEquals( [1,2,3].removeAt(0), [2,3] )
assertEquals( [1,2,3].removeLast(), [1,2] )
>>> void

There is a way to remove a range (see Range for more on ranges):

assertEquals( [1, 4], [1,2,3,4].removeRange(1..2))
assertEquals( [1, 4], [1,2,3,4].removeRange(1..<3))
>>> void

Open end ranges remove head and tail elements:

assertEquals( [3, 4, 5], [1,2,3,4,5].removeRange(..1))
assertEquals( [3, 4, 5], [1,2,3,4,5].removeRange(..<2))
assertEquals( [1, 2], [1,2,3,4,5].removeRange( (2..) ))
>>> void

Comparisons

assert( [1, 2] != [1, 3])
assert( [1, 2, 3] > [1, 2])
assert( [1, 3] > [1, 2, 3])
assert( [1, 2, 3] == [1, 2, 3])
assert( [1, 2, 3] != [1, 2, "three"])
// note that in the case above objects are referentially different:
assert( [1, 2, 3] !== [1, 2, 3])
>>> void

In-place sort

List could be sorted in place, just like [Collection] provide sorted copies, in a very like way:

val l1 = [6,3,1,9]
l1.sort()
assertEquals( [1,3,6,9], l1)

l1.sortBy { -it }
assertEquals( [1,3,6,9].reversed(), l1)

l1.sort() // 1 3 6 9
l1.sortBy { it % 4 }
// 1,3,6,9 gives, mod 4:
// 1 3 2 1
// we hope we got it also stable:
assertEquals( [1,9,6,3], l1)
>>> void

Members

name	meaning	type
size	current size	Int
add(elements...)	add one or more elements to the end	Any
insertAt(index,elements...)	insert elements at position	Int, Any
removeAt(index)	remove element at position	Int
remove(from,toNonInclusive)	remove range from (incl) to (nonincl)	Int, Int
remove(Range)	remove range	Range
removeLast()	remove last element
removeLast(n)	remove n last elements	Int
contains(element)	check the element is in the list (1)
[index]	get or set element at index	Int
[Range]	get slice of the array (copy)	Range
+=	append element(s) (2)	List or Obj
sort()	in-place sort, natural order	void
'sortBy(predicate)`	in place sort bu predicate call result (3)	void
`SortWith(comparator)	in place sort using comarator function (4)	void

(1)

optimized implementation that override Array one

(2)

+= append either a single element, or all elements if the List or other Iterable instance is appended. If you want to append an Iterable object itself, use add instead.

(3)

predicate is called on each element, and the returned values are used to sort in natural order, e.g. is same as list.sortWith { a,b -> predicate(a) <=> predicate(b) }

(4)

comparator callable takes tho arguments and must return: negative value when first is less, positive if first is greater, and zero if they are equal. For example, the equvalent comparator for sort() will be `sort { a, b -> a <=> b }

It inherits from Iterable too and thus all iterable methods are applicable to any list.

Member inherited from Array

name	meaning	type
last	last element (throws if empty)
lastOrNull	last element or null
lastIndex		Int
indices	range of indexes	Range
contains(item)	test that item is in the list

(1)

end-inclisiveness allows to use negative indexes to, for exampe, remove several last elements, like list.removeRangeInclusive(-2, -1) will remove two last elements.