X-Git-Url: http://git.megacz.com/?p=coq-hetmet.git;a=blobdiff_plain;f=examples%2Ftutorial.hs;h=7668eab785d33c7cf8912e6e2a687bda02883e8f;hp=1ac97ae3265eb7bb200b161be2bf33a4f3c2fab4;hb=e3e2ce9cb83acdd8191049b4e9bd3d4fcf6a4db4;hpb=70939a4eb9560ceeea3e9cf176ac5a36f9201ac4 diff --git a/examples/tutorial.hs b/examples/tutorial.hs index 1ac97ae..7668eab 100644 --- a/examples/tutorial.hs +++ b/examples/tutorial.hs @@ -384,7 +384,7 @@ class GuestStream g a where class GuestEqChar g where <[ (==) ]> :: <[ Char -> Char -> Bool ]>@g -{- + staged_accept :: Regex -> forall c s. @@ -419,7 +419,7 @@ staged_accept (Const c) k = <[ \s -> if gs_empty s then false else (gs_head s) == ~~(guestCharLiteral c) && ~~k (gs_tail s) ]> --} + -- this type won't work unless the case for (Star e) is commented out; -- see loop above @@ -441,7 +441,12 @@ staged_accept (Const c) k = -------------------------------------------------------------------------------- -- Unflattening -{- +-- The current implementation has problems with literals at level>0; +-- there are special-purpose hacks for Int and Char, but none for +-- unit. So I use this instead as a placeholder for <[ () ]> + +<[ u ]> = Prelude.error "FIXME" + -- This more or less "undoes" the flatten function. People often ask -- me how you "translate generalized arrows back into multi-level -- terms".. I'm not sure why you'd want to do that, but this is how: @@ -451,17 +456,16 @@ instance Category Code where id = Code <[ \x -> x ]> f . g = Code <[ \x -> ~~(unCode f) (~~(unCode g) x) ]> -instance GArrow Code (,) where +instance GArrow Code (,) () where ga_first f = Code <[ \(x,y) -> ((~~(unCode f) x),y) ]> ga_second f = Code <[ \(x,y) -> (x ,(~~(unCode f) y)) ]> ga_cancell = Code <[ \(_,x) -> x ]> ga_cancelr = Code <[ \(x,_) -> x ]> - ga_uncancell = Code <[ \x -> (%%(),x) ]> - ga_uncancelr = Code <[ \x -> (x,%%()) ]> + ga_uncancell = Code <[ \x -> (u,x) ]> + ga_uncancelr = Code <[ \x -> (x,u) ]> ga_assoc = Code <[ \((x,y),z) -> (x,(y,z)) ]> ga_unassoc = Code <[ \(x,(y,z)) -> ((x,y),z) ]> --} @@ -496,14 +500,10 @@ instance GArrow g (**) u => GArrow (GArrowInversePair g (**) u) (**) u where ga_unassoc = GArrowInversePair { forward = ga_unassoc , backward = ga_assoc } instance GArrowSwap g (**) u => GArrowSwap (GArrowInversePair g (**) u) (**) u where ga_swap = GArrowInversePair { forward = ga_swap , backward = ga_swap } -{- -instance (GArrowDrop g (**) u, GArrowCopy g (**) u) => GArrowCopy (GArrowInversePair g (**) u) (**) u where - ga_copy = GArrowInversePair { forward = ga_copy , backward = ga_second ga_drop >>> ga_cancelr } --} -- but notice that we can't (in general) get -- instance GArrowDrop g => GArrowDrop (GArrowInversePair g) where ... -{- + -- For that, we need PreLenses, which "log the history" where necessary. -- I call this a "PreLens" because it consists of the data required -- for a Lens (as in BCPierce's Lenses) but does not necessarily @@ -515,7 +515,7 @@ instance Category PreLens where id = PreLens { preLens = \x -> (x, (\x -> x)) } f . g = PreLens { preLens = \x -> let (gx,g') = (preLens g) x in let (fgx,f') = (preLens f) gx in (fgx , \q -> g' (f' q)) } -instance GArrow PreLens (,) where +instance GArrow PreLens (,) () where ga_first f = PreLens { preLens = \(x,z) -> let (y,f') = (preLens f) x in ((y,z),(\(q1,q2) -> (f' q1,q2))) } ga_second f = PreLens { preLens = \(z,x) -> let (y,f') = (preLens f) x in ((z,y),(\(q1,q2) -> (q1,f' q2))) } ga_cancell = PreLens { preLens = \(_,x) -> (x, (\x -> ((),x))) } @@ -525,25 +525,25 @@ instance GArrow PreLens (,) where ga_assoc = PreLens { preLens = \((x,y),z) -> ( (x,(y,z)) , (\(x,(y,z)) -> ((x,y),z)) ) } ga_unassoc = PreLens { preLens = \(x,(y,z)) -> ( ((x,y),z) , (\((x,y),z) -> (x,(y,z))) ) } -instance GArrowDrop PreLens (,) where +instance GArrowDrop PreLens (,) () where ga_drop = PreLens { preLens = \x -> (() , (\() -> x)) } -instance GArrowCopy PreLens (,) where +instance GArrowCopy PreLens (,) () where ga_copy = PreLens { preLens = \x -> ((x,x) , fst) } -instance GArrowSwap PreLens (,) where +instance GArrowSwap PreLens (,) () where ga_swap = PreLens { preLens = \(x,y) -> ((y,x) , (\(z,q) -> (q,z))) } data Lens x y where Lens :: forall x y c1 c2 . ((x,c1)->(y,c2)) -> ((y,c2)->(x,c1)) -> Lens x y - +{- -- can we make lenses out of GArrows other than (->)? instance Category Lens where id = Lens (\x -> x) (\x -> x) (Lens g1 g2) . (Lens f1 f2) = Lens (\(x,(c1,c2)) -> let (y,fc) = f1 (x,c1) in let (z,gc) = g1 (y,c2) in (z,(fc,gc))) (\(z,(c1,c2)) -> let (y,gc) = g2 (z,c2) in let (x,fc) = f2 (y,c1) in (x,(fc,gc))) -instance GArrow Lens (,) where +instance GArrow Lens (,) () where ga_first (Lens f1 f2) = Lens (\((x1,x2),c) -> let (y,c') = f1 (x1,c) in ((y,x2),c')) (\((x1,x2),c) -> let (y,c') = f2 (x1,c) in ((y,x2),c')) ga_second (Lens f1 f2) = Lens (\((x1,x2),c) -> let (y,c') = f1 (x2,c) in ((x1,y),c')) @@ -561,20 +561,19 @@ instance GArrow Lens (,) where ga_unassoc = Lens (\((x,(y,z)),()) -> (((x,y),z),())) (\(((x,y),z),()) -> ((x,(y,z)),())) -instance GArrowDrop Lens (,) where +instance GArrowDrop Lens (,) () where ga_drop = Lens (\(x,()) -> ((),x)) (\((),x) -> (x,())) -instance GArrowCopy Lens (,) where +instance GArrowCopy Lens (,) () where ga_copy = Lens (\(x,()) -> ((x,x),())) (\((x,_),()) -> (x,())) -instance GArrowSwap Lens (,) where +instance GArrowSwap Lens (,) () where ga_swap = Lens (\((x,y),()) -> ((y,x),())) (\((x,y),()) -> ((y,x),())) -instance BiGArrow Lens (,) where +instance BiGArrow Lens (,) () where biga_arr f f' = Lens (\(x,()) -> ((f x),())) (\(x,()) -> ((f' x),())) biga_inv (Lens f1 f2) = Lens f2 f1 -} - -------------------------------------------------------------------------------- -- An example generalized arrow