just what I was looking for, thanks! 2012/8/20 Erik Hesselink <hessel...@gmail.com>: > Untested, but this should be about right: > > osi (Bij f b) = iso (Bij b f) > > Erik > > On Mon, Aug 20, 2012 at 2:35 PM, Sergey Mironov <ier...@gmail.com> wrote: >> Hi. I'm porting old code, which uses fclabels <0.5. Old fclabels >> define Iso typeclass as follows: >> >> class Iso f where >> iso :: a :<->: b -> f a -> f b >> iso (Lens a b) = osi (b <-> a) >> osi :: a :<->: b -> f b -> f a >> osi (Lens a b) = iso (b <-> a) >> >> Newer one defines iso: >> >> class Iso (~>) f where >> iso :: Bijection (~>) a b -> f a ~> f b >> >> instance Arrow (~>) => Iso (~>) (Lens (~>) f) where >> iso bi = arr ((\a -> lens (fw bi . _get a) (_set a . first (bw bi))) . >> unLens) >> >> instance Arrow (~>) => Iso (~>) (Bijection (~>) a) where >> iso = arr . (.) >> >> but no osi. I'm not a guru in categories, can you help me define osi? >> >> Thanks >> Sergey. >> >> _______________________________________________ >> Haskell-Cafe mailing list >> Haskell-Cafe@haskell.org >> http://www.haskell.org/mailman/listinfo/haskell-cafe
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