Re: [Haskell-cafe] Invertible functions list

Use operator precedence: infixr . I don't remember exactly how it is used, but it should do the trick and let you get rid of the parentheses. 2009/12/29 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 wrote:

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On Mon, Dec 28, 2009 at 10:32 PM, Jonathan Fischoff wrote:

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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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