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elk/libraries/Array.elm
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1module Array where
3{-| A library for immutable arrays. The elements in an array must have the same
4type. The arrays are implemented in Relaxed Radix Balanced-Trees for fast
5reads, updates, and concatenation.
7If you use more then one map or zip function on an array, consider turning it
8into a list before operating on it, and then turning it back into an array.
10# Basics
11@docs empty, length, get, getMaybe, getSafe
13# Putting Arrays Together
14@docs fill, fromList, concat, set, updates, push
16# Taking Arrays Apart
17@docs toList, toIndexedList, indices, slice
19# Mapping, folding, zipping
20@docs map, indexedMap, foldl, foldr, zip, zipWith
21-}
23import Native.Array
24import Basics (..)
25import Maybe (..)
26import List
28data Array a = Array
30{-| Fills an array with a given length and a default element.
32 fill 3 5 == fromList [5,5,5]
33-}
34fill : Int -> a -> Array a
35fill len e = fromList <| List.map (always e) [1..len]
37-- TODO: make this a native function.
38{-| Create an array from a list. -}
39fromList : [a] -> Array a
40fromList = List.foldl (Native.Array.push) Native.Array.empty
42{-| Create a list of elements from an array.
44 toList (fromList [3,5,8]) == [3,5,8]
45-}
46toList : Array a -> [a]
47toList = Native.Array.toList
49{-| Create a list of the possible indices of an array.
51 indices (fromList [3,5,8] == [0,1,2])
52-}
53indices : Array a -> [Int]
54indices a = [0..Native.Array.length a - 1]
56-- TODO: make this a native function.
57{-| Create a list of tuples (Index, Element) from an array.
59 toIndexedList (fromList [3,5,8]) == [(0,3), (1,5), (2,8)]
60-}
61toIndexedList : Array a -> [(Int, a)]
62toIndexedList a = List.zip (indices a) (Native.Array.toList a)
64{-| Apply a function on every element in an array.
66 map (\x -> x*x) (fromList [1,2,3]) == fromList [1,4,9]
67-}
68map : (a -> b) -> Array a -> Array b
69map = Native.Array.map
71{-| Apply a function on every element with its index as first argument.
73 indexedMap (*) (fromList [5,5,5]) == fromList [0,5,10]
74-}
75indexedMap : (Int -> a -> b) -> Array a -> Array b
76indexedMap = Native.Array.indexedMap
78{-| Reduce an array from the left.
80 foldl (+) 0 (fill 3 5) == 15
81-}
82foldl : (a -> b -> b) -> b -> Array a -> b
83foldl = Native.Array.foldl
85{-| Reduce an array from the right.
87 foldr (::) [] (fromList [1,2,3]) == [3,2,1]
88-}
89foldr : (a -> b -> b) -> b -> Array a -> b
90foldr = Native.Array.foldr
92{-| Zip the elements of two arrays via a tuple into a new array. If one array is
93longer, the extra elements are dropped.
95 zip (fromList [1,2,3,4]) (fromList [0,0,0]) = fromList [(1,0), (2,0), (3,0)]
96-}
97zip : Array a -> Array b -> Array (a,b)
98zip = zipWith (,)
100{-| Zips the elements of two arrays via a function into a new array. If one array
101is longer, the extra elements are dropped.
103 zipWith (+) (fill 3 5) (fill 5 8) == fill 3 13
104-}
105zipWith : (a -> b -> c) -> Array a -> Array b -> Array c
106zipWith f a b =
107 fromList <| List.zipWith f (Native.Array.toList a) (Native.Array.toList b)
109{-| Return an empty array.
111 length empty == 0
112-}
113empty : Array a
114empty = Native.Array.empty
116{-| Push an element to the end of an array.
118 push 3 (fromList [1,2]) == fromList [1,2,3]
119-}
120push : a -> Array a -> Array a
121push = Native.Array.push
123{-| Return the element at the index. Breaks, if index is out of range. If the
124array length is unkown, use safeGet oder getWithDefault.
126 get 2 (A.fromList [3,2,1]) == 1
127-}
128get : Int -> Array a -> a
129get = Native.Array.get
131{-| Return Just the element at the index or Nothing if the index is out of range.
133 getMaybe 2 (A.fromList [3,2,1]) == Just 2
134 getMaybe 5 (A.fromList [3,2,1]) == Nothing
135-}
136getMaybe : Int -> Array a -> Maybe a
137getMaybe i array = if Native.Array.length array > i
138 then Just (Native.Array.get i array)
139 else Nothing
141{-| Get the element at the index. If the index is out of range, the given default
142element is returned.
144 getSafe 0 2 (A.fromList [3,2,1]) == 1
145 getSafe 0 5 (A.fromList [3,2,1]) == 0
146-}
147getSafe : a -> Int -> Array a -> a
148getSafe default i array = if Native.Array.length array > i
149 then Native.Array.get i array else default
151{-| Set the element at the index. Returns the updated array, or if the index is
152out of range, the unaltered array.
154 set 1 7 (fromList [1,2,3]) == fromList [1,7,3]
155-}
156set : Int -> a -> Array a -> Array a
157set = Native.Array.set
159{-| Update an array with a a list tuples, wherein the first Int is the index.
161 updates [(1,7),(2,8)] (fill 3 1) == fromList [1,7,8]
162-}
163updates : [(Int, a)] -> Array a -> Array a
164updates us array = List.foldl (uncurry Native.Array.set) array us
166{-| Slice an array given a range. The selection is inclusive, so the last
167element in the selection will also be in the new array. This may change in the
168future.
169You can select from the end by giving a negative Int.
171 slice 1 2 (fromList [0,1,2,3,4]) == fromList [1,2]
172 slice 1 -2 (fromList [0,1,2,3,4]) == fromList [1,2,3]
173 slice -3 -2 (fromList [0,1,2,3,4]) == fromList [2,3]
174-}
175slice : Int -> Int -> Array a -> Array a
176slice = Native.Array.slice
178{-| Return the length of an array.
180 length (fromList [1,2,3]) == 3
181-}
182length : Array a -> Int
183length = Native.Array.length
185{-| Concat two arrays to a new one.
187 concat (fill 3 1) (fill 4 2) == fromList [1,1,1,2,2,2,2]
188-}
189concat : Array a -> Array a -> Array a
190concat = Native.Array.concat