sierpinski.hs

{-
In the beginning, we simply print a triangle which points upwards. 
There are 32 rows and 63 columns in this matrix. 
The triangle is composed of underscores and ones as shown below.-}

{-# LANGUAGE OverloadedRecordDot #-}

import Data.Bits
import Data.Colour.CIE.Illuminant (c)

type CanvasLine = Integer
type Canvas = [CanvasLine]


data Triangle = Triangle { top :: Int, center :: Int, height :: Int ,  inverted :: Bool}

    
canvas :: Canvas
canvas = replicate 32 zeroBits

canvasLine :: [Int] -> CanvasLine
canvasLine = foldl setBit zeroBits 

triangle :: Triangle -> [CanvasLine]
triangle t = align $ map lines (take  t.height [0..]) where
    lines i = canvasLine [t.center - i .. t.center + i]
    align = if t.inverted then reverse else id

addTriangle :: Triangle -> Canvas -> Canvas
addTriangle t c = aboveLines ++ middleLines ++ belowLines where
    aboveLines = take t.top c
    middleLines = zipWith xor (triangle t)  (drop t.top c)
    belowLines = drop (t.top + t.height) c

-- takes a triangle and returns information for the 4 triangles it produces in next iteration
centerTriangle :: Triangle -> Triangle
centerTriangle = undefined 

edgeTriangles :: Triangle -> [Triangle]
edgeTriangles = undefined

-- IO functions

main :: IO ()
main = do 
    let c = canvas 
    printCanvas c
    let t1 = Triangle {top = 0, center = 31, height = 32, inverted = False}
        c1 = addTriangle t1 c
    printCanvas c1
    let t2 = Triangle {top = 16, center = 31, height = 16, inverted = True}
        c2 = addTriangle t2 c1
    printCanvas c2


printCanvas :: Canvas -> IO ()    
printCanvas t = newLine >> mapM_ printLine t >> newLine 

printLine :: CanvasLine -> IO ()
printLine l = mapM_ (printPoint l) [0..62] >> newLine where
    printPoint l i = putStr $ if l `testBit` i  then  "1" else "_" 

newLine :: IO ()
newLine = putStrLn ""