[Haskell-cafe] Invertible functions list

[Jonathan Fischoff]

Thirst will work I think. I tested a demo and the only problem I can see is
the unwieldiness of the syntax, i.e

testThirst = f `Cons` (g `Cons` (h `Cons` Nil))

Maybe there is a way to sugar up the syntax to get rid of the parentheses?

On Mon, Dec 28, 2009 at 7:43 PM, Antoine Latter <aslatter at gmail.com> wrote:

> On Mon, Dec 28, 2009 at 10:32 PM, Jonathan Fischoff
> <jonathangfischoff at gmail.com> wrote:
> > Hi,
> > I would to create a list of tuples (or something similar) of invertible
> > functions
> > [((a -> b), (b -> a)), ((b -> c), (c -> b)), ....
> > Such that I could call
> > forward invertibleFuctionList domainValue = ? -- composite all the
> functions
> > backward invertibleFuctionList rangeValue =
> >     forward (reverse invertibleFuctionList) rangeValue  -- or something
> > similar
> >
> > I would also like to concat them. This sounds like a job for GADT that
> > someone might have already tackled. Any ideas?
>
> It looks like the thrist package should help you out:
>
> http://hackage.haskell.org/cgi-bin/hackage-scripts/package/thrist
>
> You could define some sort of type Iso:
>
> data Iso a b = Iso (a -> b) (b -> a)
>
> And then build a Thrist and fold over it, the functions forward and
> backwards can both be implemented with right-folds.
>
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