Re: [Haskell-cafe] [ANN] anonymous-sums

* Omari Norman [2014-02-15 08:46:06-0500]

On Fri, Feb 14, 2014 at 11:02 PM, Tikhon Jelvis wrote:

...

Yeah, S0 and S1 are probably worth including for the sake of completion. We don't have a 1-tuple, and I believe that's caused a bit of trouble for people writing generic libraries. Enough trouble so that somebody wrote a OneTuple package[1] anyhow.

S1 is easy enough; I added that in.

http://hackage.haskell.org/package/anonymous-sums-0.2.2.0

S0 takes some more thought as there's more than one way to do that. I could use EmptyDataDecls or do it more like ekmett's Data.Void. Then what do you get for, e.g., partitionS0?

partitionS0 :: [S0] -> ()

I suppose that makes sense if you look at partition as returning the same number of lists as there are type variables. No type variables, no lists. Or should it be

partitionS0 :: [S0] -> Void

which also makes me wonder if this is a special case better left to Data.Void.

The result should be a 0-tuple, i.e. (), of course. Otherwise, what would paritionS0 [] return? Roman