N00b Haskell Matrix library (unready)

Main.hs

module Main where

import System.Environment (getArgs)
import Data.List
import Matrix
import IO

main :: IO ()
main = do
    hSetBuffering stdout NoBuffering
    a <- putStr "Add meg a file nevét: "
    fileName <- getLine
    putStr "Add meg a kvadratikus mátrix méretét: "
    size <- getLine
    file <- openFile fileName WriteMode
    hPutMatrix file (identityMatrix (read size)) 
    hClose file
    return ()

Matrix.hs

module Matrix where

import Data.List
import IO

identityMatrix :: Int -> [[Int]]
identityMatrix 0 = [[]]
identityMatrix n = [identityVector n x | x <- [1..n]]

identityVector :: Int -> Int -> [Int]
identityVector x n = [if a == n then 1 else 0 | a <- [1..x]]

checkMatrix :: [[a]] -> Bool
checkMatrix m = and (map (== (head rowLengths)) (tail rowLengths))
    where
        rowLengths = map length m

isQuadratic :: [[a]] -> Bool
isQuadratic m | checkMatrix m
            = length m == length (m !! 0)
{-
- Determinant of a 2 by 2 matrix.
- Ex.: det2x2 [[0,1],[1,0]]  -- => 1
-}
det2x2 :: [[Int]] -> Int
det2x2 m | isQuadratic m && length m == 2
         -- a*d - b*c
         = (m !! 0 !! 0) * (m !! 1 !! 1) 
         - (m !! 0 !! 1) * (m !! 1 !! 0)

matrixRowAndCol :: [[Int]] -> (Int, Int)
matrixRowAndCol m | checkMatrix m
                  = (length m, length (m !! 0))

-- Impure functions

hPutVector :: Handle -> [Int] -> IO ()
hPutVector h v = hPutStr h (intercalate " " (map show v))

hPutMatrix :: Handle -> [[Int]] -> IO ()
hPutMatrix h [] = return ()
hPutMatrix h (x:xs) = do 
                    hPutVector h x 
                    hPutChar h '\n'
                    hPutMatrix h xs