31 lines
790 B
Haskell
31 lines
790 B
Haskell
import Text.Printf (printf)
|
|
import Control.Monad (when)
|
|
|
|
factorial :: Integral n => n -> n
|
|
factorial 0 = 1
|
|
factorial n = product [1..n]
|
|
|
|
lah :: Integral n => n -> n -> n
|
|
lah n k
|
|
| k == 1 = factorial n
|
|
| k == n = 1
|
|
| k > n = 0
|
|
| k < 1 || n < 1 = 0
|
|
| otherwise = f n `div` f k `div` factorial (n - k)
|
|
where
|
|
f = (*) =<< (^ 2) . factorial . pred
|
|
|
|
printLah :: (Word, Word) -> IO ()
|
|
printLah (n, k) = do
|
|
when (k == 0) (printf "\n%3d" n)
|
|
printf "%11d" (lah n k)
|
|
|
|
main :: IO ()
|
|
main = do
|
|
printf "Unsigned Lah numbers: L(n, k):\nn/k"
|
|
mapM_ (printf "%11d") zeroToTwelve
|
|
mapM_ printLah $ (,) <$> zeroToTwelve <*> zeroToTwelve
|
|
printf "\nMaximum value from the L(100, *) row:\n%d\n"
|
|
(maximum $ lah 100 <$> ([0..100] :: [Integer]))
|
|
where zeroToTwelve = [0..12]
|