HackerRank.com - Functional Programming - Haskell - Compute The Area Of A Polygon

a_compute_the_area_of_a_polygon.hs

main = do
    raw <- getContents -- readFile "input.txt"
    let toInts a = map (\e -> read e :: Int) a
        noded = map toInts $ map words $ tail $ lines raw
        nodec = length noded
        xdata = map head noded
        ydata = map last noded
        sum1x = xdata
        sum1y = (tail ydata) ++ [head ydata]
        sum2x = (tail xdata) ++ [head xdata]
        sum2y = ydata
        sum1 = sum $ map (\(a, b) -> a * b) $ zip sum1x sum1y
        sum2 = sum $ map (\(a, b) -> a * b) $ zip sum2x sum2y
        sumN = abs $ sum1 - sum2
        sumF = (fromIntegral sumN) / 2
    putStrLn $ show sumF
    
    

input.txt

8
458 695
621 483
877 469
1035 636
1061 825
875 1023
645 1033
485 853

output.txt

255931.0