Efficient way to code "(symbol,multiplicity)-counting" - how?

[Dylan Thurston]

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On Thu, May 23, 2002 at 04:44:25PM +0930, Mark Phillips wrote:
=2E..
> We "count" as follows:
> [] [x] [y] [z] [x,y] [x,z] [y,x] [y,y] [y,z] [z,x] [z,y] [x,y,y] [x,y,z]
> [x,z,y] [y,x,y] [y,x,z] [y,y,x] [y,y,z] [y,z,x] [y,z,y] [z,x,y] [z,y,x]
> [z,y,y] [x,y,y,z] [x,y,z,y] [x,z,y,y] [y,x,y,z] [y,x,z,y] [y,y,x,z]
> [y,y,z,x] [y,z,x,y] [y,z,y,x] [z,x,y,y] [z,y,x,y] [z,y,y,x]
> and then start back at the beginning again (with []).
>=20
> I want to define a function
> next :: [(a,Int)] -> [a] -> [a]

Is there a reason you frame the problem this way?  Would it be OK to
give a function

> count :: [(a,Int)] -> [[a]]

which would return, e.g., the list you gave above?  That would
probably be more natural to code.

--Dylan Thurston

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