On Mon, Feb 2, 2009 at 11:39 AM, Creighton Hogg <wchogg@gmail.com> wrote:
2009/1/29 Conal Elliott <conal@conal.net>:
> Hi Achim,
>
> I came to the same conclusion: I want to sweep aside these OO, imperative
> toolkits, and replace them with something "genuinely functional", which for
> me means having a precise & simple compositional (denotational) semantics.
> Something meaningful, formally tractable, and powefully compositional from
> the ground up.  As long as we build on complex legacy libraries (Gtk,
> wxWidgets, Qt, OpenGL/GLUT, ...), we'll be struggling against (or worse yet,
> drawn into) their ad hoc mental models and system designs.
>
> As Meister Eckhart said, "Only the hand that erases can write the true
> thing."

I think working on a purely functional widget toolkit would actually
be a really cool project.  Do you have any ideas, though, on what
should be the underlying primitives?

Again, my goal would not be a "purely functional" library, because even IO is "purely functional".  My goal is a "denotational" library, i.e., one that has an elegant (denotational) semantics, and hence is powerfully compositional and good for reasoning.

The initial gut feeling I have is that one should just ignore any
notion of actually displaying widgets & instead focus on a clean
algebra of how to 'add'  widgets that relates the concepts of
inheritance & relative position.  What I mean by inheritance, here, is
how to direct a flow of 'events'.  I don't necessarily mean events in
the Reactive sense, because I think it'd be important to make the
model completely independent of how time & actual UI actions are
handled.

Any thoughts to throw in, here?

Cheers,
C


The Fruit paper, "Genuinely Functional User Interfaces", gives a semantic model, which could be a starting place for thinking about possibilities.  At the very least, I'd like to take it to 3D.  The idea there is that a UI is a function from flows (behaviors/signals) to flows, where the input includes mouse & keyboard stuff and the output includes an image.  An image is, as in Pan, a function from R^2 -> Color, where color includes partial opacity.  When UIs are transformed in time and/or space, they correspondingly see inversely-transformed input, thanks to a general principle of transforming functions.

   - Conal