enumFromThenTo package:base

Used in Haskell's translation of [n,n'..m] with [n,n'..m] = enumFromThenTo n n' m, a possible implementation being enumFromThenTo n n' m = worker (f x) (c x) n m, x = fromEnum n' - fromEnum n, c x = bool (>=) ((x 0)

f n y
| n > 0 = f (n - 1) (succ y)
| n < 0 = f (n + 1) (pred y)
| otherwise = y

and

worker s c v m
| c v m = v : worker s c (s v) m
| otherwise = []

Examples

• enumFromThenTo 4 2 -6 :: [Integer] =
  [4,2,0,-2,-4,-6]

• enumFromThenTo 6 8 2 :: [Int] = []