-- Array with access by a given index

-- The type of arrays containing elements of type `a`:
type Array a = (Int -> a)

-- The empty array:
emptyArray :: Array a
emptyArray i = error "Undefined index position!"

-- Put an element at an index into an array:
putIndex :: Array a -> Int -> a -> Array a
putIndex a i v = a'
 where a' j | i == j    = v
            | otherwise = a j

-- Get an element at an index position in an array: selector a[i]
getIndex :: Array a -> Int -> a
getIndex a i = a i

ar12 :: Array Int
ar12 = putIndex (putIndex emptyArray 1 42) 2 99

initArray :: a -> Array a
--initArray v = const v
initArray = const

arHello :: Array String
arHello = putIndex (putIndex (initArray "") 1 "Hello") 2 "world"