9 Jan
2006
9 Jan
'06
4:56 a.m.
David F. Place wrote:
main' n = let p = permutations [1..n] in do mapM_ (putStrLn . concatMap show) $ take 30 p putStr $ "Pfannkuchen(" ++ show n ++ ") = " putStrLn . show $ foldl' (flip (max . steps 0)) 0 p
In the original version, the author called 'permutations' twice and didn't create a variable binding.
As a side note, I expected GHC to do common subexpression elimination and evaluate permutations [1..n] only once, caching the 30 results that are used twice. I didn't try to find out whether it actually did though. Bertram