Array slice

Main.purs

module Main where

import Prelude
import Data.Array as Array
import Partial.Unsafe (unsafePartial)

data Slice a = Slice (Array a) Int Int

fromArray :: forall a. Array a -> Slice a
fromArray arr = Slice arr 0 (Array.length arr)

toArray :: forall a. Slice a -> Array a
toArray (Slice arr beg end)
  | beg == 0 && end == Array.length arr =
      arr
  | otherwise =
      Array.slice beg end arr
  
data Uncons a
  = Cons a (Slice a)
  | Nil

uncons :: forall a. Slice a -> Uncons a
uncons (Slice arr beg end)
  | beg == end =
      Nil
  | otherwise =
      unsafePartial $ Cons (Array.unsafeIndex arr beg) (Slice arr (beg + 1) end)