Bresenham's line drawing algorithm

import List (sort,unfoldr)

type Point = (Integer,Integer)

line :: Point -> Point -> [Point]
line pa@(xa,ya) pb@(xb,yb) = map maySwitch . unfoldr go $ (x1,y1,0)
  where
    steep = abs (yb - ya) > abs (xb - xa)
    maySwitch = if steep then (\(x,y) -> (y,x)) else id
    [(x1,y1),(x2,y2)] = sort [maySwitch pa, maySwitch pb]
    deltax = x2 - x1
    deltay = abs (y2 - y1)
    ystep = if y1 < y2 then 1 else -1
    go (xTemp, yTemp, error)
        | xTemp > x2 = Nothing
        | otherwise  = Just ((xTemp, yTemp), (xTemp + 1, newY, newError))
        where
          tempError = error + deltay
          (newY, newError) = if (2*tempError) >= deltax
                            then (yTemp+ystep,tempError-deltax)
                            else (yTemp,tempError)

Thanks to Cheddai Fouche for the above implementation.

The core logic is in the "go" function which is passed to unfoldr.

And here is an implementation of generalized Bresenham's line drawing algorithm, in terms of balanced words: https://github.com/LambdaHack/LambdaHack/blob/2f031f8a09d07d46b8e0dfeff1d9653d31ea19cc/Game/LambdaHack/Common/Point.hs#L112