# class sys::List

sys::Obj
sys::List

List represents an linear sequence of Objects indexed by an Int.

See examples.

@Operator

Add the specified item to the end of the list. The item will have an index of size. Size is incremented by 1. Return this. Throw ReadonlyErr if readonly.

Add all the items in the specified list to the end of this list. Size is incremented by list.size. Return this. Throw ReadonlyErr if readonly.

Call add if item is non-null otherwise do nothing. Return this.

all

Bool all(|V,Int->Bool| c)

Return true if c returns true for all of the items in the list. If the list is empty, return true. This method is readonly safe.

Example:

list := ["ant", "bear"]
list.all |Str v->Bool| { return v.size >= 3 } => true
list.all |Str v->Bool| { return v.size >= 4 } => false
any

Bool any(|V,Int->Bool| c)

Return true if c returns true for any of the items in the list. If the list is empty, return false. This method is readonly safe.

Example:

list := ["ant", "bear"]
list.any |Str v->Bool| { return v.size >= 4 } => true
list.any |Str v->Bool| { return v.size >= 5 } => false
binaryFind

Int binaryFind(|V,Int->Int| c)

Find an element in the list using a binary search algorithm. The specified comparator function returns a negative integer, zero, or a positive integer if the desired object is less than, equal to, or greater than specified item. The list must be sorted in ascending order according to the specified comparator function. If the key is not found, then return a negative value which is -(insertation point) - 1.

binarySearch

Int binarySearch(V key, |V,V->Int|? c := null)

Search the list for the index of the specified key using a binary search algorithm. The list must be sorted in ascending order according to the specified comparator function. If the list contains multiple matches for key, no guarantee is made to which one is returned. If the comparator is null then then it is assumed to be the <=> operator (shortcut for the compare method). If the key is not found, then return a negative value which is -(insertation point) - 1.

capacity

Int capacity

The number of items this list can hold without allocating more memory. Capacity is always greater or equal to size. If adding a large number of items, it may be more efficient to manually set capacity. See the trim method to automatically set capacity to size. Throw ArgErr if attempting to set capacity less than size. Getting capacity is readonly safe, setting capacity throws ReadonlyErr if readonly.

L clear()

Remove all items from the list and set size to 0. Return this. Throw ReadonlyErr if readonly.

contains

Bool contains(V item)

Return if this list contains the specified item. Equality is determined by Obj.equals. This method is readonly safe.

containsAll

Bool containsAll(L list)

Return if this list contains every item in the specified list. Equality is determined by Obj.equals. This method is readonly safe.

containsAny

Bool containsAny(L list)

Return if this list contains any one of the items in the specified list. Equality is determined by Obj.equals. This method is readonly safe.

containsSame

Bool containsSame(V item)

Return if this list contains the specified item. Equality is determined by ===. This method is readonly safe.

dup

L dup()

Create a shallow duplicate copy of this List. The items themselves are not duplicated. The resulting list is always read/write. This method is readonly safe.

each

Void each(|V,Int| c)

Call the specified function for every item in the list starting with index 0 and incrementing up to size-1. This method is readonly safe.

Example:

["a", "b", "c"].each |Str s| { echo(s) }
eachRange

Void eachRange(Range r, |V,Int| c)

Iterate the list usnig the specified range. Negative indexes may be used to access from the end of the list. This method is readonly safe. Throw IndexErr if range is invalid.

eachWhile

Obj? eachWhile(|V,Int->Obj?| c)

Iterate every item in the list starting with index 0 up to size-1 until the function returns non-null. If function returns non-null, then break the iteration and return the resulting object. Return null if the function returns null for every item. This method is readonly safe.

eachr

Void eachr(|V,Int| c)

Reverse each - call the specified function for every item in the list starting with index size-1 and decrementing down to 0. This method is readonly safe.

Example:

["a", "b", "c"].eachr |Str s| { echo(s) }
eachrWhile

Obj? eachrWhile(|V,Int->Obj?| c)

Reverse eachWhile. Iterate every item in the list starting with size-1 down to 0. If the function returns non-null, then break the iteration and return the resulting object. Return null if the function returns null for every item. This method is readonly safe.

equals

virtual override Bool equals(Obj? that)

Two Lists are equal if they have the same type, the same number of items, and all the items at each index return true for equals.

Examples:

[2, 3] == [2, 3]     =>  true
[2, 3] == [3, 2]     =>  false
[2, 3] == Num[2, 3]  =>  false
Str[,] == [,]        =>  false
Str[,] == Str?[,]    =>  false
exclude

L exclude(|V,Int->Bool| c)

Return a new list containing the items for which c returns false. If c returns true for every item, then return an empty list. The inverse of this method is findAll(). This method is readonly safe.

Example:

list := [0, 1, 2, 3, 4]
list.exclude |Int v->Bool| { return v%2==0 } => [1, 3]
fill

L fill(V val, Int times)

Append a value to the end of the list the given number of times. Return this. Throw ReadonlyErr if readonly.

Example:

Int[,].fill(0, 3)  =>  [0, 0, 0]
find

V? find(|V,Int->Bool| c)

Return the first item in the list for which c returns true. If c returns false for every item, then return null. This method is readonly safe.

Example:

list := [0, 1, 2, 3, 4]
list.find |Int v->Bool| { return v.toStr == "3" } => 3
list.find |Int v->Bool| { return v.toStr == "7" } => null
findAll

L findAll(|V,Int->Bool| c)

Return a new list containing the items for which c returns true. If c returns false for every item, then return an empty list. The inverse of this method is exclude(). This method is readonly safe.

Example:

list := [0, 1, 2, 3, 4]
list.findAll |Int v->Bool| { return v%2==0 } => [0, 2, 4]
findIndex

Int? findIndex(|V,Int->Bool| c)

Return the index of the first item in the list for which c returns true. If c returns false for every item, then return null. This method is readonly safe.

Example:

list := [5, 6, 7]
list.findIndex |Int v->Bool| { return v.toStr == "7" } => 2
list.findIndex |Int v->Bool| { return v.toStr == "9" } => null
findNotNull

L findNotNull()

Return a new list with all null items removed. The returned list will be based on this list's type but non-nullable. This method is readonly safe.

Example:

list := Int?[1, null, 2, null, 3]
list.findNotNull => Int[1, 2, 3]
findType

L findType(Type t)

Return a new list containing all the items which are an instance of the specified type such that item.type.fits(t) is true. Any null items are automatically excluded. If none of the items are instance of the specified type, then an empty list is returned. The returned list will be a list of t. This method is readonly safe.

Example:

list := ["a", 3, "foo", 5sec, null]
list.findType(Str#) => Str["a", "foo"]
first

V? first()

Return the item at index 0, or if empty return null. This method is readonly safe.

flatMap

Obj?[] flatMap(|V,Int->Obj?[]| c)

This is a combination of map and flatten. Each item in this list is mapped to zero or more new items by the given function and the results are returned in a single flattened list. Note unlike flatten only one level of flattening is performed. The new list is typed based on the return type of c. This method is readonly safe.

Example:

list := ["a", "b"]
list.flatMap |v->Str[]| { [v, v.upper] } => ["a", "A", "b", "B"]
flatten

Obj?[] flatten()

Return a new list which recursively flattens any list items into a one-dimensional result. This method is readonly safe.

Examples:

[1,2,3].flatten        =>  [1,2,3]
[[1,2],[3]].flatten    =>  [1,2,3]
[1,[2,[3]],4].flatten  =>  [1,2,3,4]
get

@Operator
V get(Int index)

Get is used to return the item at the specified the index. A negative index may be used to access an index from the end of the list. For example get(-1) is translated into get(size()-1). The get method is accessed via the [] shortcut operator. Throw IndexErr if index is out of range. This method is readonly safe.

getRange

@Operator
L getRange(Range range)

Return a sub-list based on the specified range. Negative indexes may be used to access from the end of the list. This method is accessed via the [] operator. This method is readonly safe. Throw IndexErr if range illegal.

Examples:

list := [0, 1, 2, 3]
list[0..2]   => [0, 1, 2]
list[3..3]   => [3]
list[-2..-1] => [2, 3]
list[0..<2]  => [0, 1]
list[1..-2]  => [1, 2]
getSafe

V? getSafe(Int index, V? def := null)

Get the item at the specified index, but if index is out of range, then return def parameter. A negative index may be used according to the same semantics as get. This method is readonly safe.

hash

virtual override Int hash()

Return platform dependent hashcode based a hash of the items of the list.

index

Int? index(V item, Int offset := 0)

Return the integer index of the specified item using the == operator (shortcut for equals method) to check for equality. Use indexSame to find with === operator. The search starts at the specified offset and returns the first match. The offset may be negative to access from end of list. Throw IndexErr if offset is out of range. If the item is not found return null. This method is readonly safe.

indexSame

Int? indexSame(V item, Int offset := 0)

Return integer index just like List.index except use === same operator instead of the == equals operator.

indexr

Int? indexr(V item, Int offset := -1)

Reverse index lookup. This method works just like index except that it searches backward from the starting offset.

insert

L insert(Int index, V item)

Insert the item at the specified index. A negative index may be used to access an index from the end of the list. Size is incremented by 1. Return this. Throw IndexErr if index is out of range. Throw ReadonlyErr if readonly.

insertAll

L insertAll(Int index, L list)

Insert all the items in the specified list into this list at the specified index. A negative index may be used to access an index from the end of the list. Size is incremented by list.size. Return this. Throw IndexErr if index is out of range. Throw ReadonlyErr if readonly.

intersection

L intersection(L that)

Return a new list which is the intersection of this list and the given list. The intersection is defined as the unique items which are in both lists. The new list will be ordered according to this list's order. The new list is guaranteed to be unique with no duplicate values. Equality is determined using hash() and the == operator (shortcut for equals method). This method is readonly safe.

Example:

[0, 1, 2, 3].intersection([5, 3, 1]) => [1, 3]
[0, null, 2].intersection([null, 0, 1, 2, 3]) => [0, null, 2]
isEmpty

Bool isEmpty()

Return if size == 0. This method is readonly safe.

isRO

Bool isRO()

Return if this List is readonly. A readonly List is guaranteed to be immutable (although its items may be mutable themselves). Any attempt to modify a readonly List will result in ReadonlyErr. Use rw to get a read-write List from a readonly List. Methods documented as "readonly safe" may be used safely with a readonly List. This method is readonly safe.

isRW

Bool isRW()

Return if this List is read-write. A read-write List is mutable and may be modified. Use ro to get a readonly List from a read-write List. This method is readonly safe.

join

Str join(Str separator := "", |V,Int->Str|? c := null)

Return a string by concatenating each item's toStr result using the specified separator string. If c is non-null then it is used to format each item into a string, otherwise Obj.toStr is used. This method is readonly safe.

Example:

["a", "b", "c"].join => "abc"
["a", "b", "c"].join("-") => "a-b-c"
["a", "b", "c"].join("-") |Str s->Str| { return "(\$s)" } => "(a)-(b)-(c)"
last

V? last()

Return the item at index-1, or if empty return null. This method is readonly safe.

make

new make(Type of, Int capacity)

Constructor with of type and initial capacity.

makeObj

new makeObj(Int capacity)

Constructor for Obj?[] with initial capacity.

map

Obj?[] map(|V,Int->Obj?| c)

Create a new list which is the result of calling c for every item in this list. The new list is typed based on the return type of c. This method is readonly safe.

Example:

list := [3, 4, 5]
list.map |Int v->Int| { return v*2 } => [6, 8, 10]
mapNotNull

Obj[] mapNotNull(|V,Int->Obj?| c)

Convenience for map and findNotNull. Each item is mapped by the given function and if null is returned it is excluded from the result. The resulting type is based on on the return type of c but non-nullable. This method is readonly safe.

Example:

list := [3, 4, 5]
list.mapIfNotNull |Int v->Int?| { v.isOdd ? 10+v : null } => [13, 15]
max

V? max(|V,V->Int|? c := null)

Return the maximum value of the list. If c is provided, then it implements the comparator returning -1, 0, or 1. If c is null then the <=> operator is used (shortcut for compare method). If the list is empty, return null. This method is readonly safe.

Example:

list := ["albatross", "dog", "horse"]
list.max => "horse"
list.max |Str a, Str b->Int| { return a.size <=> b.size } => "albatross"
min

V? min(|V,V->Int|? c := null)

Return the minimum value of the list. If c is provided, then it implements the comparator returning -1, 0, or 1. If c is null then the <=> operator is used (shortcut for compare method). If the list is empty, return null. This method is readonly safe.

Example:

list := ["albatross", "dog", "horse"]
list.min => "albatross"
list.min |Str a, Str b->Int| { return a.size <=> b.size } => "dog"
moveTo

L moveTo(V? item, Int toIndex)

Find the given item, and move it to the given index. All the other items are shifted accordingly. Negative indexes may used to access an index from the end of the list. If the item is null or not found then this is a no op. Return this. Throw ReadonlyErr if readonly.

Examples:

[10, 11, 12].moveTo(11, 0)  =>  [11, 10, 12]
[10, 11, 12].moveTo(11, -1) =>  [10, 12, 11]
of

Type of()

Get the item Type of this List.

Examples:

["hi"].of    =>  Str#
[[2, 3]].of  =>  Int[]#
peek

V? peek()

Return the item at index-1, or if empty return null. This method has the same semantics as last(). This method is readonly safe.

pop

V? pop()

Remove the last item and return it, or return null if the list is empty. This method as the same semantics as removeAt(-1), with the exception that an empty list is handled. Throw ReadonlyErr if readonly.

push

L push(V item)

Add the specified item to the end of the list. Return this. This method has the same semantics as add(item). Throw ReadonlyErr if readonly.

random

V? random()

Return a random item from the list. If the list is empty return null. This method is readonly safe. Also see Int.random, Float.random, Range.random, and Random.

reduce

Obj? reduce(Obj? init, |Obj?,V,Int->Obj?| c)

Reduce is used to iterate through every item in the list to reduce the list into a single value called the reduction. The initial value of the reduction is passed in as the init parameter, then passed back to the closure along with each item. This method is readonly safe.

Example:

list := [1, 2, 3]
list.reduce(0) |Obj r, Int v->Obj| { return (Int)r + v } => 6
remove

V? remove(V item)

Remove the specified value from the list. The value is compared using the == operator (shortcut for equals method). Use removeSame to remove with the === operator. Return the removed value and decrement size by 1. If the value is not found, then return null. Throw ReadonlyErr if readonly.

removeAll

L removeAll(L list)

Remove every item in this list which is found in the toRemove list using same semantics as remove (compare for equality via the == operator). If any value is not found, it is ignored. Return this. Throw ReadonlyErr if readonly.

removeAt

V removeAt(Int index)

Remove the object at the specified index. A negative index may be used to access an index from the end of the list. Size is decremented by 1. Return the item removed. Throw IndexErr if index is out of range. Throw ReadonlyErr if readonly.

removeRange

L removeRange(Range r)

Remove a range of indices from this list. Negative indexes may be used to access from the end of the list. Throw ReadonlyErr if readonly. Throw IndexErr if range illegal. Return this (*not* the removed items).

removeSame

V? removeSame(V item)

Remove the item just like remove except use the === operator instead of the == equals operator.

reverse

L reverse()

Reverse the order of the items of this list in-place. Return this. Throw ReadonlyErr if readonly.

Example:

[1, 2, 3, 4].reverse  =>  [4, 3, 2, 1]
ro

L ro()

Get a readonly List instance with the same contents as this List (although the items may be mutable themselves). If this List is already readonly, then return this. Only methods documented as "readonly safe" may be used safely with a readonly List, all others will throw ReadonlyErr. This method is readonly safe. See Obj.isImmutable and Obj.toImmutable for deep immutability.

rw

L rw()

Get a read-write, mutable List instance with the same contents as this List. If this List is already read-write, then return this. This method is readonly safe.

set

@Operator
L set(Int index, V item)

Set is used to overwrite the item at the specified the index. A negative index may be used to access an index from the end of the list. The set method is accessed via the []= shortcut operator. If you wish to use List as a sparse array and set values greater then size, then manually set size larger. Return this. Throw IndexErr if index is out of range. Throw ReadonlyErr if readonly.

shuffle

L shuffle()

Shuffle this list's items into a randomized order. Return this. Throw ReadonlyErr if readonly.

size

Int size

The number of items in the list. Getting size is readonly safe, setting size throws ReadonlyErr if readonly.

If the size is set greater than the current size then the list is automatically grown to be a sparse list with new items defaulting to null. However if this is a non-nullable list, then growing a list will throw ArgErr.

If the size is set less than the current size then any items with indices past the new size are automatically removed. Changing size automatically allocates new storage so that capacity exactly matches the new size.

sort

L sort(|V,V->Int|? c := null)

Perform an in-place sort on this list. If a method is provided it implements the comparator returning -1, 0, or 1. If the comparator method is null then sorting is based on the value's <=> operator (shortcut for compare method). Return this. Throw ReadonlyErr if readonly.

Example:

s := ["candy", "ate", "he"]

s.sort
// s now evaluates to [ate, candy, he]

s.sort |Str a, Str b->Int| { return a.size <=> b.size }
// s now evaluates to ["he", "ate", "candy"]
sortr

L sortr(|V,V->Int|? c := null)

Reverse sort - perform an in-place reverse sort on this list. If a method is provided it implements the comparator returning -1, 0, or 1. If the comparator method is null then sorting is based on the items <=> operator (shortcut for compare method). Return this. Throw ReadonlyErr if readonly.

Example:

[3, 2, 4, 1].sortr =>  [4, 3, 2, 1]
swap

L swap(Int indexA, Int indexB)

Swap the items at the two specified indexes. Negative indexes may used to access an index from the end of the list. Return this. Throw ReadonlyErr if readonly.

toCode

Str toCode()

Get this list as a Fantom expression suitable for code generation. The individual items must all respond to the toCode method.

toStr

virtual override Str toStr()

Return a string representation the list. This method is readonly safe.

trim

L trim()

Trim the capacity such that the underlying storage is optimized for the current size. Return this. Throw ReadonlyErr if readonly.

union

L union(L that)

Return a new list which is the union of this list and the given list. The union is defined as the unique items which are in either list. The resulting list is ordered first by this list's order, and secondarily by that's order. The new list is guaranteed to be unique with no duplicate values. Equality is determined using hash() and the == operator (shortcut for equals method). This method is readonly safe.

Example:

[1, 2].union([3, 2]) => [1, 2, 3]
unique

L unique()

Returns a new list with all duplicate items removed such that the resulting list is a proper set. Duplicates are detected using hash() and the == operator (shortcut for equals method). This method is readonly safe.

Example:

["a", "a", "b", "c", "b", "b"].unique => ["a", "b", "c"]