On Mon, Feb 06, 2006 at 03:05:45AM +1100, skaller wrote:
> On Sun, 2006-02-05 at 15:17 +0100, Oliver Bandel wrote:
> 
> Looking at 
> 
> http://www.belug.org/~ob/struktur-grafisch.jpg
> 
> the bottom diagram, I would do this:
> 
> type state = { e:t; u:t }
> 
> for some type t I don't know about, possibly the types
> are different, but this will do for exposition.
> 
> You also have arrows
> 
> 	a: t * t -> t
> 	b: t * t -> t
> 	c: t -> t
[...]


Ah, OK, that's fine to start with the type! :)

Starting the task with the type clarifies a lot! :)



> 
> So the clock function is simply
> 
> 	let step (s:state) x =
> 	{ s with 
> 		e = c s.u;
> 		u = b (x, s.e)
> 	} 
> 	in s, a (x, s.e)

OK, that's nice... I had forgotten how (but knew that I once knew
that it must be possible) to make a functional record-update-copy.
The "with" keyword is a fine thing. :)
Looks so much smaller the code, much nicer than the let...in stuff :)


> 
> This function accepts the state and a new input x,
> and returns the state and the output y. 

OK, I will explore it.

Thanks.


Ciao,
   Oliver