[Haskell] Arrows GUI Library Based on GTK+

[Kevin Atkinson]

On Sat, 19 Mar 2005 ross at soi.city.ac.uk wrote:

> On Sat, Mar 19, 2005 at 07:48:09AM -0700, Kevin Atkinson wrote:

> > Has anyone tried to make Fudgets an instance of the Arrow class?
> 
> see the stream processors in John Hughes's original paper.

I will have a closer look.

> > > - how about: data Event a = NoEvent | Event a
> > 
> > And what would "a" be?
> 
> The thing you currently always pair with an Event, and ignore if it's
> NoEvent.

But that value may also be used even if there is not an event.  For 
example you may want to read the current value of an Entry or a 
ToggleButton.

> > > - you don't really need mkAFunDef in AbstractFunction, and indeed you
> > >   don't need AbstractFunction either -- you could just use Arrow, of
> > >   which both (->) and FG are already instances.
> > 
> > But than can I make a function like "tag" which can either be used as an 
> > arrow or a function.
> 
> But functions are arrows: (->) is an instance of the Arrow class.

But of separate Arrow instances.  For example if I redefine tag from

  tag :: (AbstractFunction f) => b -> f (Event, a) (Event, b)
  tag v = mkAFun (\(e, _) -> (e, v)) 
to
  tag :: b -> (Event, a) -> (Event, b)
  tag v = \(e, _) -> (e, v)

Than I couldn't do as I gave in my example:

  a <- tag "a" <<< button [] -< def

-- 
http://kevin.atkinson.dhs.org