On Tue, 22 Mar 2005, Kevin Atkinson wrote:
On Sun, 20 Mar 2005 ross@soi.city.ac.uk wrote:
On Sat, Mar 19, 2005 at 12:17:46PM -0700, Kevin Atkinson wrote:
On Sat, 19 Mar 2005 ross@soi.city.ac.uk 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/.
Make that http://kevin.atkinson.dhs.org/fg/. Sorry need to pay attention when I paste URL's :( -- http://kevin.atkinson.dhs.org