Re: [Haskell-cafe] Why binding to existing widget toolkits doesn't make any sense

On Mon, Feb 2, 2009 at 3:28 PM, Conal Elliott wrote:

On Mon, Feb 2, 2009 at 11:39 AM, Creighton Hogg wrote:

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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.

Well, that is essentially what I meant but your point about clarity is taken. A truly mathematical semantic model is above & beyond what is meant by "purely functional".

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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.

Thanks. I'm reading it now. Cheers, C