iota.hs

{-# LANGUAGE FlexibleInstances #-}

-- iota of SRFI-1

iota1 n = [0 .. n-1]
iota2 n m = [m .. m+n-1]
iota3 n m s = [m, m+s .. m+s*(n-1)]

class PType t where
  iota :: t

instance PType (Int -> [Int]) where
  iota = iota1

instance PType (Int -> Int -> [Int]) where
  iota = iota2

instance PType (Int -> Int -> Int -> [Int]) where
  iota = iota3

main = do
  print $ (iota (3 :: Int) :: [Int])
  print $ (iota (3 :: Int) (10 :: Int) :: [Int])
  print $ (iota (3 :: Int) (10 :: Int) (-2 :: Int) :: [Int])