Henning,

i need the bi-partitions of a multiset. That is, all the ways you can split a multiset, M, into two multisets, M1 and M2, such that M = M1 `multiset-union` M2.

Best wishes,

--greg

On 5/23/07, Henning Thielemann <lemming@henning-thielemann.de> wrote:

On Tue, 22 May 2007, Greg Meredith wrote:

> mSplitC :: [a] -> [([a], [a])] -- C for comprehension
>
> mSplitC [] = [([],[])]
> mSplitC [x] = [([x],[])]
> mSplitC (x:xs) = concat [ [(x:l,r),(l,x:r)] | (l,r) <- mSplitC xs ]
>
> which Matthias Radestock suggested to me.
>
> Note that if you only supply the empty multiset case, then you end up with
> duplicates.

That is ([1,2],[3]) and ([3],[1,2]) are considered the same? But you need
always pairs not only [1,2] and [3] ?



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