mandel.hs

{-# LANGUAGE BangPatterns #-}
--Enables strict arguments, the X in mandelbrot

import Data.Complex
import Data.List

maxIter :: Int
maxIter = 50

xMin, xMax, xPrecision, yMin, yMax, yPrecision :: Double
xMin = -2 -- -2
xMax = 1 -- 1
xPrecision = 0.001 -- 0.05
yMin = -1.25 -- -2
yMax = 1.25 -- 2
yPrecision = 0.001 -- 0.05

mandelbrot :: Complex Double -> Complex Double -> Int -> Int
mandelbrot !x !c !iter
    | magnitude f >= 2 = iter
    | iter >= maxIter = -1
    | otherwise = mandelbrot f c (iter + 1)
    where f = x ^ 2 + c

applyColormap :: [[Int]] -> [[[Int]]]
applyColormap = (map . map) color
    where color n
            | n == (-1) = [0]
            | otherwise = [n]

mandelColormapString :: String
mandelColormapString = (unlines . map (unwords . map (unwords . map show))) $ applyColormap mandelSet
    where mandelSet = (map . map) (\c -> mandelbrot 0 c 0) [[a :+ b | a <- [xMin, (xMin+xPrecision) .. xMax]] | b <- [yMax, (yMax-yPrecision) .. yMin]] -- for whatever reason the y's are backwards. it works, don't change it

header :: String
header = "P2\n"++(show $ length [xMin, (xMin+xPrecision) .. xMax])++" "++(show $ length [yMax, (yMax-yPrecision) .. yMin])++"\n"++(show maxIter)++"\n"

file :: String
file = header ++ mandelColormapString

main :: IO ()
main = writeFile "mandelbrot.pgm" file