is there documentation on these Generators?

i only know the Timothy Budd variety
     from LittleSmalltalk
     i guess his variety of Generator
          was used extensively in LittleSmalltalk




On Wed, Apr 12, 2017 at 09:52 Levente Uzonyi <leves at caesar.elte.hu> wrote:

> Wouldn't it be better to make Generator >> #do: not use #atEnd?
> With the new implementation the following happens:
>
> | generator |
> generator := Generator on: [ :g | ].
> generator atEnd
> "==> false"
>
> | generator |
> generator := Generator on: [ :g | ].
> generator next; atEnd
> "==> true"
>
> Also, this change set will break existing Generator instances if you load
> them into your image and it happens to have some.
>
> Levente
>
> On Wed, 12 Apr 2017, Bert Freudenberg wrote:
>
> > Hi all,
> > there was an interesting question about Generators on StackOverflow:
> >
> >
> http://stackoverflow.com/questions/43340007/yield-prolog-adaptation-for-smalltalk
> >
> > It's about a pseudo-Prolog implementation using Generators and yield.
> >
> > Our Generator *almost* works for this, except there is a little problem
> with the timing of side-effects:
> >
> > | x gen |
> > x := 0.
> >
> > gen := Generator on: [:g |
> > x := 1.
> > g yield: nil.
> >
> > x := 2.
> > g yield: nil.
> >
> > x := 3.
> > g yield: nil].
> >
> > gen do: [:i | Transcript cr; show: x].
> >
> > This *should* print '1 2 3' but actually prints '2 3 3'. This is because
> our Generator is written to support a streaming interface (using atEnd
> > and peek) so it always computes one yield ahead.
> >
> > In other languages (e.g. JavaScript, Python, C#) this is different, the
> execution is paused at the current yield statement, not 'before' the next
> > one. In general, a generator cannot know if there will be more "yields"
> without executing more code. In Javascript, 'next' returns both a value
> > and a 'done' flag, and if the flag is true, the returned value must not
> be used.
> >
> > IMHO we should fix this - see attached changeset Marcel and I came up
> with. We did not fix the tests yet, but the behavior seems right.
> >
> > Even though generators are in the image for a long time they are not
> used widely yet (AFAIK) so maybe we can still change the behavior? What do
> > people think?
> >
> > - Bert & Marcel -
> >
> >
> >
>
>
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