[Haskell-cafe] map over Bijections

[Erik Hesselink]

If you remove the second argument (which you don't use), you have the
function `liftBij` that is in fclabels.

Erik

On Mon, Aug 27, 2012 at 3:55 PM, Sergey Mironov <ierton at gmail.com> wrote:
> Hi. I need map equivalent for Bijection type which is defined in fclabels:
>
> data Bijection (~>) a b = Bij { fw :: a ~> b, bw :: b ~> a }
>
> instance Category (~>) => Category (Bijection (~>)) where ...
>
> I can define this function as follows:
> mapBij :: Bijection (->) a c -> Bijection (->) [a] [b] -> Bijection (->) [a] [c]
> mapBij b1 b = (map (fw b1)) `Bij` (map (bw b1))
>
> but do I really need to do it explicitly? Can I obtain same result
> using some Category combinators or other common stuff?
>
> Sergey
>
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