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elk/libraries/Array.elm
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1module Array where
3{-| A library for manipulating arrays of elements. The elements in an
4array must have the same type. The arrays are implemented in Relaxed
5Radix Balanced-Trees for fast updating and concating.
7If you use more then one map or zip function on an array, consider turning it
8first into a list, operating on it, and then turning it back into an array.
10# Basics
11@docs empty, length, get, safeGet, getWithDefault
13# Putting Arrays Together
14@docs fill, fromList, concat, set, updates, push
16# Taking Arrays Apart
17@docs elements, indices, assocs, slice
19# Mapping, folding, zipping
20@docs map, assocMap, 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{-| Create an array from a list. -}
38fromList : [a] -> Array a
39fromList = List.foldl (Native.Array.push) Native.Array.empty
41{-| Create a list of elements from an array.
43 elements (fromList [3,5,8]) == [3,5,8]
44-}
45elements : Array a -> [a]
46elements = Native.Array.toList
48{-| Create a list of the possible indices of an array.
50 indices (fromList [3,5,8] == [0,1,2])
51-}
52indices : Array a -> [Int]
53indices a = [0..Native.Array.length a - 1]
55{-| Create a list of tuples (Index, Element) from an array.
57 assocs (fromList [3,5,8]) == [(0,3), (1,5), (2,8)]
58-}
59assocs : Array a -> [(Int, a)]
60assocs a = List.zip (indices a) (Native.Array.elements a)
62{-| Apply a function on every element in an array.
64 map (\x -> x*x) (fromList [1,2,3]) == fromList [1,4,9]
65-}
66map : (a -> b) -> Array a -> Array b
67map = Native.Array.map
69{-| Apply a function with an index on every element in an array.
71 assocMap (*) (fromList [5,5,5]) == fromList [0,5,10]
72-}
73assocMap : (Int -> a -> b) -> Array a -> Array b
74assocMap = Native.Array.assocMap
76{-| Reduce an array from the left.
78 foldl (+) 0 (fill 3 5) == 15
79-}
80foldl : (a -> b -> b) -> b -> Array a -> b
81foldl = Native.Array.foldl
83{-| Reduce an array from the right.
85 foldr (::) [] (fromList [1,2,3]) == [3,2,1]
86-}
87foldr : (a -> b -> b) -> b -> Array a -> b
88foldr = Native.Array.foldr
90{-| Zip the elements of two arrays via a tuple into a new array. If one array is
91longer, the extra elements are dropped.
93 zip (fromList [1,2,3,4]) (fromList [0,0,0]) = fromList [(1,0), (2,0), (3,0)]
94-}
95zip : Array a -> Array b -> Array (a,b)
96zip = zipWith (,)
98{-| Zips the elements of two arrays via a function into a new array. If one array
99is longer, the extra elements are dropped.
101 zipWith (+) (fill 3 5) (fill 5 8) == fill 3 13
102-}
103zipWith : (a -> b -> c) -> Array a -> Array b -> Array c
104zipWith f a b =
105 fromList <| List.zipWith f (Native.Array.elements a) (Native.Array.elements b)
107{-| Return an empty array.
109 length empty == 0
110-}
111empty : Array a
112empty = Native.Array.empty
114{-| Push an item to the end of an array.
116 push 3 (fromList [1,2]) == fromList [1,2,3]
117-}
118push : a -> Array a -> Array a
119push = Native.Array.push
121{-| Return the value at the index. Breaks, if index is out of range. If the
122array length is unkown, use safeGet oder getWithDefault.
124 get 2 (A.fromList [3,2,1]) == 1
125-}
126get : Int -> Array a -> a
127get = Native.Array.get
129{-| Return Just the element at the index or Nothing.
131 safeGet 2 (A.fromList [3,2,1]) == Just 2
132 safeGet 5 (A.fromList [3,2,1]) == Nothing
133-}
134safeGet : Int -> Array a -> Maybe a
135safeGet i array = if Native.Array.length array > i
136 then Just (Native.Array.get i array)
137 else Nothing
139{-| Get the element at the index. If the index is out of range, the given default
140elementis returned.
142 getWithDefault 0 2 (A.fromList [3,2,1]) == 1
143 getWithDefault 0 5 (A.fromList [3,2,1]) == 0
144-}
145getWithDefault : a -> Int -> Array a -> a
146getWithDefault default i array = if Native.Array.length array > i
147 then Native.Array.get i array else default
149{-| Set the element at the index. Returns the updated array, or if the index is
150out of range, the unaltered array.
152 set 1 7 (fromList [1,2,3]) == fromList [1,7,3]
153-}
154set : Int -> a -> Array a -> Array a
155set = Native.Array.set
157{-| Update an array with a a list tuples, wherein the first Int is the index.
159 updates [(1,7),(2,8)] (fill 3 1) == fromList [1,7,8]
160-}
161updates : [(Int, a)] -> Array a -> Array a
162updates assocs array = List.foldl (uncurry Native.Array.set) array assocs
164{-| Slice an array given a range. The selection is inclusive, so the last
165element in the selection will also be in the new array. This may change in the
166future.
167You can select from the end by giving a negative Int.
169 slice 1 2 (fromList [0,1,2,3,4]) == fromList [1,2]
170 slice 1 -2 (fromList [0,1,2,3,4]) == fromList [1,2,3]
171 slice -3 -2 (fromList [0,1,2,3,4]) == fromList [2,3]
172-}
173slice : Int -> Int -> Array a -> Array a
174slice = Native.Array.slice
176{-| Return the length of an array.
178 length (fromList [1,2,3]) == 3
179-}
180length : Array a -> Int
181length = Native.Array.length
183{-| Concat two arrays to a new one.
185 concat (fill 3 1) (fill 4 2) == fromList [1,1,1,2,2,2,2]
186-}
187concat : Array a -> Array a -> Array a
188concat = Native.Array.concat