Re: [stack] Generators revisited

On Nov 13, 2007, at 19:20 , William Tanksley, Jr wrote:

> Don Groves <[email protected]> wrote:
>> In rethinking the design of generators, it occurred to me that a
>> generator is in fact a closure. I'm not familiar enough with the
>> literature yet to know if closures already have an accepted
>> methodology in this group, so please enlighten me if this is so.
>
> Sure is! Actually, I kinda assumed that was going to be how you'd
> implement them :-).

I may be slow at times but I eventually catch up ;-)


>> A generator might look like [[f] a b ..] where f is the generation
>> function and a, b, etc, are its static data.  A new combinator,
>> generate (as suggested by Billy), would be needed which would
>> disassemble the generator; apply f to the the list [a b ..];
>> reassemble the generator; and push the new value on the stack.
>
> Yup. It's a simple enough function to define.
>
> The hard part is building all of the 'f's you might need. It's
> impossible to build them all; in general you have to let programmers
> build 'em for you. Icon takes one route (by making expressions be
> capable of repeating themselves); anyone know any others?

Sure, a few simple ones could be built in (Z for example) but others
would be up to users to define as needed. I'm implementing a
Fibonacci generator in ACL at the moment to serve as an example.
--
Don


>> Don Groves
>
> -Billy