Plot simple y(x) functions in ASCII

Plot.hs

-- * Plot simple y(x) functions in ASCII
--
import Control.Monad
import Control.Arrow
import Control.Monad.ST
import Data.Array.ST
import Data.Array.Unboxed
import qualified Data.Array.ST as AS
import qualified Data.Array.MArray as AM
import Data.Ord
import Data.Function
import qualified Data.List as L


type Range  = (Double, Double)
type Points = [(Double, Double)]

data Plot
  = Plot
  { plotWidth  :: Int
  , plotHeight :: Int
  , plotPoints :: [(Double, Double)] }
  deriving Show

plotToArray :: Plot -> UArray (Int, Int) Char
plotToArray (Plot width height points)
  = AS.runSTUArray
  $ do let maxX   = L.maximum $ fmap fst points
           maxY   = L.maximum $ fmap snd points
           scaleX = maxX / fromIntegral width
           scaleY = maxY / fromIntegral height
           scaled = fmap ((/scaleX) *** (/scaleY)) points
       a <- AM.newArray ((0,0), (width + 1, height + 1)) ' '
       forM_ scaled
         $ \(x,y) -> AM.writeArray a (round x, height - round y) 'x'
       return a

printArray :: UArray (Int, Int) Char -> IO ()
printArray a
  = do let (minB, maxB) = bounds a
           row i        = [ a ! (x, i) | x <- [fst minB .. snd maxB] ]
           thing        = fmap row [snd minB .. snd maxB]
       mapM_ putStrLn thing