Hi Paul, I don't have time to solve your actual problem, but I think it's doable using associated type families. I attach a module which I'm using in my current project that does things quite similar to what you're asking for. For example: *Main> replicateArray (3 :> IntArr) 4 [4,4,4] *Main> replicateArray (4 :> 3 :> IntArr) 4 [[4,4,4],[4,4,4],[4,4,4],[4,4,4]] Hope it helps! / Emil Paul Keir skrev:
Hi all,
If I have a list, and I'd like to convert it to a list of lists, each of length n, I can use a function like bunch:
bunch _ [] = [] bunch n as = let (c,cs) = splitAt n as in c:bunch n cs
bunch 8 [1..16] [[1,2,3,4,5,6,7,8],[9,10,11,12,13,14,15,16]]
If I now want to do the same for the nested lists, I can compose an application involving both map and bunch:
map (bunch 4) . bunch 8 $ [1..16] [[[1,2,3,4],[5,6,7,8]],[[9,10,11,12],[13,14,15,16]]]
and I can "bunch" the new length 4 lists again:
map (map (bunch 2)) . map (bunch 4) . bunch 8 $ [1..16] [[[[1,2],[3,4]],[[5,6],[7,8]]],[[[9,10],[11,12]],[[13,14],[15,16]]]]
Clearly there is a pattern here involving the bunch function and latterly, three Int parameters; 2, 4 and 8. My question is, can I create a function that will take such parameters as a list, and give the same result, for example:
f [2,4,8] [1..16] [[[[1,2],[3,4]],[[5,6],[7,8]]],[[[9,10],[11,12]],[[13,14],[15,16]]]]
or perhaps:
f [bunch 2, bunch 4, bunch 8] [1..16] [[[[1,2],[3,4]],[[5,6],[7,8]]],[[[9,10],[11,12]],[[13,14],[15,16]]]]
I think it may not be possible because the type signature of f would depend on the length of its list parameter; but I'm not sure.
-Paul
------------------------------------------------------------------------
_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe