haskellstriangle.hs

{-- 1
   1 1
  1 2 1
 1 3 3 1
1 4 6 4 1 --}


-- printRow :: (Integral a, Show a) => a -> [a] -> IO ()
printRow :: Int -> [Int] -> IO ()
printRow pad nums = let printPad c = putStr [' ' | _ <- [1..c]]
                    in do
                        printPad pad
                        putStrLn [x | ent <- nums, x <- ((show ent) ++ " " )]


-- genRow :: (Integral a) => [a] -> [a]
genRow :: [Int] -> [Int]
genRow prev = [1] ++ newRow ++ [1]
            where newRow = zipWith (+) prev (tail prev)


-- couldn't define a type signature here like i wanted to
-- build :: (Integral a, Show a) => [a] -> a -> IO ()
build :: [Int] -> Int -> IO ()
build row size
    | padding < 0 = putChar '\n'
    | otherwise = do
                   printRow padding row
                   build (genRow row) size
    where padding = size - (length row)


main = do
        putChar '\n'
        build [1] 5
        putStrLn ":^)\n"