On Fri, Nov 25, 2005 at 10:29:48AM +0100, Tomasz Zielonka wrote:
> On Thu, Nov 24, 2005 at 05:52:23PM +0100, Jan van Eijck wrote:
> > Like so:
> >
> > generatePs :: (Int,[Int]) -> [[Int]]
> > generatePs (n,[]) = [take n (repeat 1)]
> > generatePs (n,(x:xs)) =
> > (take n (repeat 1) ++ (x:xs)) : generatePs (pack (x-1) ((n+x),xs))
> > where
> > pack :: Int -> (Int,[Int]) ->(Int,[Int])
> > pack 1 (m,xs) = (m,xs)
> > pack k (m,xs) = if k > m then pack (k-1) (m,xs)
> > else pack k (m-k,k:xs)
> >
> > parts :: Int -> [[Int]]
> > parts n | n < 1 = error "part: argument <= 0"
> > | n == 1 = [[1]]
> > | otherwise = generatePs (0,[n])
>
> How about a shorter version?
>
> part :: Integer -> [[Integer]]
> part = gen 1
> where
> gen m 0 = [[]]
> gen m n = [ x:xs | x <- [m..n], xs <- gen x (n - x) ]
>
> Best regards
> Tomasz
>
Brilliant!
Jan
--
Jan van Eijck EMAIL [EMAIL PROTECTED]
CWI, PO Box 94079, 1090 GB Amsterdam, NL phone +31-20-5924052 (work)
+31-20-6250735 (home)
WWW http://www.cwi.nl/~jve fax +31-20-5924200
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