Fast immutable arrays. The elements in an array must have the same type.
Representation of fast immutable arrays. You can create arrays of integers
(Array Int
) or strings (Array String
) or any other type of value you can
dream up.
empty : Array a
Return an empty array.
length empty == 0
initialize : Basics.Int -> (Basics.Int -> a) -> Array a
Initialize an array. initialize n f
creates an array of length n
with
the element at index i
initialized to the result of (f i)
.
initialize 4 identity == fromList [0,1,2,3]
initialize 4 (\n -> n*n) == fromList [0,1,4,9]
initialize 4 (always 0) == fromList [0,0,0,0]
repeat : Basics.Int -> a -> Array a
Creates an array with a given length, filled with a default element.
repeat 5 0 == fromList [0,0,0,0,0]
repeat 3 "cat" == fromList ["cat","cat","cat"]
Notice that repeat 3 x
is the same as initialize 3 (always x)
.
fromList : List a -> Array a
Create an array from a List
.
isEmpty : Array a -> Basics.Bool
Determine if an array is empty.
isEmpty empty == True
length : Array a -> Basics.Int
Return the length of an array.
length (fromList [1,2,3]) == 3
get : Basics.Int -> Array a -> Maybe a
Return Just
the element at the index or Nothing
if the index is out of
range.
get 0 (fromList [0,1,2]) == Just 0
get 2 (fromList [0,1,2]) == Just 2
get 5 (fromList [0,1,2]) == Nothing
get -1 (fromList [0,1,2]) == Nothing
set : Basics.Int -> a -> Array a -> Array a
Set the element at a particular index. Returns an updated array. If the index is out of range, the array is unaltered.
set 1 7 (fromList [1,2,3]) == fromList [1,7,3]
push : a -> Array a -> Array a
Push an element onto the end of an array.
push 3 (fromList [1,2]) == fromList [1,2,3]
append : Array a -> Array a -> Array a
Append two arrays to a new one.
append (repeat 2 42) (repeat 3 81) == fromList [42,42,81,81,81]
slice : Basics.Int -> Basics.Int -> Array a -> Array a
Get a sub-section of an array: (slice start end array)
. The start
is a
zero-based index where we will start our slice. The end
is a zero-based index
that indicates the end of the slice. The slice extracts up to but not including
end
.
slice 0 3 (fromList [0,1,2,3,4]) == fromList [0,1,2]
slice 1 4 (fromList [0,1,2,3,4]) == fromList [1,2,3]
Both the start
and end
indexes can be negative, indicating an offset from
the end of the array.
slice 1 -1 (fromList [0,1,2,3,4]) == fromList [1,2,3]
slice -2 5 (fromList [0,1,2,3,4]) == fromList [3,4]
This makes it pretty easy to pop
the last element off of an array:
slice 0 -1 array
toList : Array a -> List a
Create a list of elements from an array.
toList (fromList [3,5,8]) == [3,5,8]
toIndexedList : Array a -> List ( Basics.Int, a )
Create an indexed list from an array. Each element of the array will be paired with its index.
toIndexedList (fromList ["cat","dog"]) == [(0,"cat"), (1,"dog")]
map : (a -> b) -> Array a -> Array b
Apply a function on every element in an array.
map sqrt (fromList [1,4,9]) == fromList [1,2,3]
indexedMap : (Basics.Int -> a -> b) -> Array a -> Array b
Apply a function on every element with its index as first argument.
indexedMap (*) (fromList [5,5,5]) == fromList [0,5,10]
foldl : (a -> b -> b) -> b -> Array a -> b
Reduce an array from the left. Read foldl
as fold from the left.
foldl (::) [] (fromList [1,2,3]) == [3,2,1]
foldr : (a -> b -> b) -> b -> Array a -> b
Reduce an array from the right. Read foldr
as fold from the right.
foldr (+) 0 (repeat 3 5) == 15
filter : (a -> Basics.Bool) -> Array a -> Array a
Keep elements that pass the test.
filter isEven (fromList [1,2,3,4,5,6]) == (fromList [2,4,6])