On Sun, 20 Mar 2005 [EMAIL PROTECTED] wrote: > On Sat, Mar 19, 2005 at 12:17:46PM -0700, Kevin Atkinson wrote: > > On Sat, 19 Mar 2005 [EMAIL PROTECTED] wrote: > > > I would also have expected loopFG to have been defined using fixIO. > > > > Could you be more specific. Ie How? > > For the type definitions > > newtype FG' a b = FG' (Control -> a -> IO (Control, b)) > newtype FG a b = FG (FGState -> IO (FG' a b, FGState)) > newtype Container a b = Container (FG ([WidgetP], a) b) > > the usual instances would be (give or take a ~): > > instance ArrowLoop FG' where > loop (FG' f) = FG' $ \ c x -> do > (c', x', _) <- mfix $ \ ~(_, _, y) -> do > ~(c', ~(x', y')) <- f c (x, y) > return (c', x', y') > return (c', x')
I must admit that I am baffled by what this is doing. But I don't think it has the semantics I want. When I try substituting your code in I get "Exception: <<loop>>". I have reworked the way loops are handled. Please have a look at the new code at http://www.haskell.org/arrows/. -- http://kevin.atkinson.dhs.org _______________________________________________ Haskell-Cafe mailing list [email protected] http://www.haskell.org/mailman/listinfo/haskell-cafe
