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

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)	List or Obj

(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.

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.

Notes

Could be rewritten using array as a class but List as the interface