Lah numbers: Difference between revisions
Content deleted Content added
m →{{header|Haskell}}: Pruning of some minor redundancy |
m →{{header|Haskell}}: Restored OP's formatting style. |
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<lang haskell>import Text.Printf (printf) |
<lang haskell>import Text.Printf (printf) |
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import Control.Monad (when) |
import Control.Monad (when) |
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factorial |
factorial :: Integral n => n -> n |
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| ⚫ | |||
=> n -> n |
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factorial 0 = 1 |
factorial 0 = 1 |
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factorial n = product [1 |
factorial n = product [1..n] |
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| ⚫ | |||
lah |
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:: Integral n |
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=> n -> n -> n |
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lah n k |
lah n k |
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| k == 1 = factorial n |
| k == 1 = factorial n |
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| k == n = 1 |
| k == n = 1 |
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| k > n = 0 |
| k > n = 0 |
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| k < 1 || n < 1 = 0 |
| k < 1 || n < 1 = 0 |
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| otherwise = f n `div` f k `div` factorial (n - k) |
| otherwise = f n `div` f k `div` factorial (n - k) |
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where |
where |
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f = (*) =<< (^ 2) . factorial . pred |
f = (*) =<< (^ 2) . factorial . pred |
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printLah :: (Word, Word) -> IO () |
printLah :: (Word, Word) -> IO () |
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printLah (n, k) = do |
printLah (n, k) = do |
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when (k == 0) (printf "\n%3d" n) |
when (k == 0) (printf "\n%3d" n) |
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printf "%11d" (lah n k) |
printf "%11d" (lah n k) |
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main :: IO () |
main :: IO () |
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main = do |
main = do |
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mapM_ (printf "%11d") zeroToTwelve |
mapM_ (printf "%11d") zeroToTwelve |
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mapM_ printLah $ (,) <$> zeroToTwelve <*> zeroToTwelve |
mapM_ printLah $ (,) <$> zeroToTwelve <*> zeroToTwelve |
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printf "\nMaximum value from the L(100, *) row:\n%d\n" |
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printf |
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(maximum $ lah 100 <$> ([0..100] :: [Integer])) |
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| ⚫ | |||
(maximum $ lah 100 <$> ([0 .. 100] :: [Integer])) |
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where |
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| ⚫ | |||
{{out}} |
{{out}} |
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<pre>Unsigned Lah numbers: L(n, k): |
<pre>Unsigned Lah numbers: L(n, k): |
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