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< title > List Class – Wren< / title >
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< h1 > < a href = "../../" > wren< / a > < / h1 >
< h2 > a classy little scripting language< / h2 >
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< li > < a href = "../" > Back to Modules< / a > < / li >
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< h2 > core classes< / h2 >
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< li > < a href = "bool.html" > Bool< / a > < / li >
< li > < a href = "class.html" > Class< / a > < / li >
< li > < a href = "fiber.html" > Fiber< / a > < / li >
< li > < a href = "fn.html" > Fn< / a > < / li >
< li > < a href = "list.html" > List< / a > < / li >
< li > < a href = "map.html" > Map< / a > < / li >
< li > < a href = "null.html" > Null< / a > < / li >
< li > < a href = "num.html" > Num< / a > < / li >
< li > < a href = "object.html" > Object< / a > < / li >
< li > < a href = "range.html" > Range< / a > < / li >
< li > < a href = "sequence.html" > Sequence< / a > < / li >
< li > < a href = "string.html" > String< / a > < / li >
< li > < a href = "system.html" > System< / a > < / li >
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< li > < a href = "bool.html" > Bool< / a > < / li >
< li > < a href = "class.html" > Class< / a > < / li >
< li > < a href = "fiber.html" > Fiber< / a > < / li >
< li > < a href = "fn.html" > Fn< / a > < / li >
< li > < a href = "list.html" > List< / a > < / li >
< li > < a href = "map.html" > Map< / a > < / li >
< li > < a href = "null.html" > Null< / a > < / li >
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< li > < a href = "num.html" > Num< / a > < / li >
< li > < a href = "object.html" > Object< / a > < / li >
< li > < a href = "range.html" > Range< / a > < / li >
< li > < a href = "sequence.html" > Sequence< / a > < / li >
< li > < a href = "string.html" > String< / a > < / li >
< li > < a href = "system.html" > System< / a > < / li >
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< main >
< h1 > List Class< / h1 >
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< p > Extends < a href = "sequence.html" > Sequence< / a > .< / p >
< p > An indexable contiguous collection of elements. More details < a href = "../../lists.html" > here< / a > .< / p >
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< h2 > Static Methods < a href = "#static-methods" name = "static-methods" class = "header-anchor" > #< / a > < / h2 >
< h3 > List.< strong > filled< / strong > (size, element) < a href = "#list.filled(size,-element)" name = "list.filled(size,-element)" class = "header-anchor" > #< / a > < / h3 >
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< p > Creates a new list with < code > size< / code > elements, all set to < code > element< / code > .< / p >
< p > It is a runtime error if < code > size< / code > is not a nonnegative integer.< / p >
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< h3 > List.< strong > new< / strong > () < a href = "#list.new()" name = "list.new()" class = "header-anchor" > #< / a > < / h3 >
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< p > Creates a new empty list. Equivalent to < code > []< / code > .< / p >
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< h2 > Methods < a href = "#methods" name = "methods" class = "header-anchor" > #< / a > < / h2 >
< h3 > < strong > add< / strong > (item) < a href = "#add(item)" name = "add(item)" class = "header-anchor" > #< / a > < / h3 >
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< p > Appends < code > item< / code > to the end of the list. Returns the added item.< / p >
< h3 > < strong > addAll< / strong > (other) < a href = "#addall(other)" name = "addall(other)" class = "header-anchor" > #< / a > < / h3 >
< p > Appends each element of < code > other< / code > in the same order to the end of the list. < code > other< / code > must be < a href = "../../control-flow.html#the-iterator-protocol" > an iterable< / a > .< / p >
< pre class = "snippet" >
var list = [0, 1, 2, 3, 4]
list.addAll([5, 6])
System.print(list) //> [0, 1, 2, 3, 4, 5, 6]
< / pre >
< p > Returns the added items.< / p >
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< h3 > < strong > clear< / strong > () < a href = "#clear()" name = "clear()" class = "header-anchor" > #< / a > < / h3 >
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< p > Removes all elements from the list.< / p >
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< h3 > < strong > count< / strong > < a href = "#count" name = "count" class = "header-anchor" > #< / a > < / h3 >
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< p > The number of elements in the list.< / p >
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< h3 > < strong > indexOf< / strong > (value) < a href = "#indexof(value)" name = "indexof(value)" class = "header-anchor" > #< / a > < / h3 >
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< p > Returns the index of < code > value< / code > in the list, if found. If not found, returns -1.< / p >
< pre class = "snippet" >
var list = [0, 1, 2, 3, 4]
System.print(list.indexOf(3)) //> 3
System.print(list.indexOf(20)) //> -1
< / pre >
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< h3 > < strong > insert< / strong > (index, item) < a href = "#insert(index,-item)" name = "insert(index,-item)" class = "header-anchor" > #< / a > < / h3 >
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< p > Inserts the < code > item< / code > at < code > index< / code > in the list.< / p >
< pre class = "snippet" >
var list = ["a", "b", "c", "d"]
list.insert(1, "e")
System.print(list) //> [a, e, b, c, d]
< / pre >
< p > The < code > index< / code > may be one past the last index in the list to append an element.< / p >
< pre class = "snippet" >
var list = ["a", "b", "c"]
list.insert(3, "d")
System.print(list) //> [a, b, c, d]
< / pre >
< p > If < code > index< / code > is negative, it counts backwards from the end of the list. It bases this on the length of the list < em > after< / em > inserted the element, so that < code > -1< / code > will append the element, not insert it before the last element.< / p >
< pre class = "snippet" >
var list = ["a", "b"]
list.insert(-1, "d")
list.insert(-2, "c")
System.print(list) //> [a, b, c, d]
< / pre >
< p > Returns the inserted item.< / p >
< pre class = "snippet" >
System.print(["a", "c"].insert(1, "b")) //> b
< / pre >
< p > It is a runtime error if the index is not an integer or is out of bounds.< / p >
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< h3 > < strong > iterate< / strong > (iterator), < strong > iteratorValue< / strong > (iterator) < a href = "#iterate(iterator),-iteratorvalue(iterator)" name = "iterate(iterator),-iteratorvalue(iterator)" class = "header-anchor" > #< / a > < / h3 >
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< p > Implements the < a href = "../../control-flow.html#the-iterator-protocol" > iterator protocol< / a > for iterating over the elements in the
list.< / p >
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< h3 > < strong > removeAt< / strong > (index) < a href = "#removeat(index)" name = "removeat(index)" class = "header-anchor" > #< / a > < / h3 >
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< p > Removes the element at < code > index< / code > . If < code > index< / code > is negative, it counts backwards
from the end of the list where < code > -1< / code > is the last element. All trailing elements
are shifted up to fill in where the removed element was.< / p >
< pre class = "snippet" >
var list = ["a", "b", "c", "d"]
list.removeAt(1)
System.print(list) //> [a, c, d]
< / pre >
< p > Returns the removed item.< / p >
< pre class = "snippet" >
System.print(["a", "b", "c"].removeAt(1)) //> b
< / pre >
< p > It is a runtime error if the index is not an integer or is out of bounds.< / p >
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< h3 > < strong > sort< / strong > (), < strong > sort< / strong > (comparer) < a href = "#sort(),-sort(comparer)" name = "sort(),-sort(comparer)" class = "header-anchor" > #< / a > < / h3 >
< p > Sorts the elements of a list in-place; altering the list. The default sort is implemented using the quicksort algorithm.< / p >
< pre class = "snippet" >
var list = [4, 1, 3, 2].sort()
System.print(list) //> [1, 2, 3, 4]
< / pre >
< p > A comparison function < code > comparer< / code > can be provided to customise the element sorting. The comparison function must return a boolean value specifying the order in which elements should appear in the list.< / p >
< p > The comparison function accepts two arguments < code > a< / code > and < code > b< / code > , two values to compare, and must return a boolean indicating the inequality between the arguments. If the function returns true, the first argument < code > a< / code > will appear before the second < code > b< / code > in the sorted results.< / p >
< p > A compare function like < code > {|a, b| true }< / code > will always put < code > a< / code > before < code > b< / code > . The default compare function is < code > {|a, b| a < b }< / code > .< / p >
< pre class = "snippet" >
var list = [9, 6, 8, 7]
list.sort {|a, b| a < b }
System.print(list) //> [6, 7, 8, 9]
< / pre >
< p > It is a runtime error if < code > comparer< / code > is not a function.< / p >
< h3 > < strong > swap< / strong > (index0, index1) < a href = "#swap(index0,-index1)" name = "swap(index0,-index1)" class = "header-anchor" > #< / a > < / h3 >
< p > Swaps values inside the list around. Puts the value from < code > index0< / code > in < code > index1< / code > ,
and the value from < code > index1< / code > at < code > index0< / code > in the list.< / p >
< pre class = "snippet" >
var list = [0, 1, 2, 3, 4]
list.swap(0, 3)
System.print(list) //> [3, 1, 2, 0, 4]
< / pre >
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< h3 > < strong > [< / strong > index< strong > ]< / strong > operator < a href = "#[index]-operator" name = "[index]-operator" class = "header-anchor" > #< / a > < / h3 >
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< p > Gets the element at < code > index< / code > . If < code > index< / code > is negative, it counts backwards from
the end of the list where < code > -1< / code > is the last element.< / p >
< pre class = "snippet" >
var list = ["a", "b", "c"]
System.print(list[1]) //> b
< / pre >
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< p > If < code > index< / code > is a < a href = "range.html" > Range< / a > , a new list is populated from the elements
in the range.< / p >
< pre class = "snippet" >
var list = ["a", "b", "c"]
System.print(list[0..1]) //> [a, b]
< / pre >
< p > You can use < code > list[0..-1]< / code > to shallow-copy a list.< / p >
< p > It is a runtime error if the index is not an integer or range, or is out of bounds.< / p >
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< h3 > < strong > [< / strong > index< strong > ]=< / strong > (item) operator < a href = "#[index]=(item)-operator" name = "[index]=(item)-operator" class = "header-anchor" > #< / a > < / h3 >
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< p > Replaces the element at < code > index< / code > with < code > item< / code > . If < code > index< / code > is negative, it counts
backwards from the end of the list where < code > -1< / code > is the last element.< / p >
< pre class = "snippet" >
var list = ["a", "b", "c"]
list[1] = "new"
System.print(list) //> [a, new, c]
< / pre >
< p > It is a runtime error if the index is not an integer or is out of bounds.< / p >
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< h3 > < strong > +< / strong > (other) operator < a href = "#+(other)-operator" name = "+(other)-operator" class = "header-anchor" > #< / a > < / h3 >
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< p > Appends a list to the end of the list (concatenation). < code > other< / code > must be < a href = "../../control-flow.html#the-iterator-protocol" > an iterable< / a > .< / p >
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< pre class = "snippet" >
var letters = ["a", "b", "c"]
var other = ["d", "e", "f"]
var combined = letters + other
System.print(combined) //> [a, b, c, d, e, f]
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< / pre >
< h3 > < strong > *< / strong > (count) operator < a href = "#\(count)-operator" name = "\(count)-operator" class = "header-anchor" > #< / a > < / h3 >
< p > Creates a new list by repeating this one < code > count< / code > times. It is a runtime error if < code > count< / code > is not a non-negative integer.< / p >
< pre class = "snippet" >
var digits = [1, 2]
var tripleDigits = digits * 3
System.print(tripleDigits) //> [1, 2, 1, 2, 1, 2]
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< / pre >
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< p > Wren lives
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< a href = "https://github.com/wren-lang/wren" > on GitHub< / a >
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— Made with ❤ by
< a href = "http://journal.stuffwithstuff.com/" > Bob Nystrom< / a > and
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< a href = "https://github.com/wren-lang/wren/blob/main/AUTHORS" > friends< / a > .
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