From: Nat Pryce <nat.pryce@...13media.com>
Date: 2001-10-14T22:02:46+09:00
Subject: [ruby-talk:22512] Re: ANN: Generator -- a class supporting lazy evaluation (Re: Open-ended ranges)

How does this differ from Knu's Generator class?  And if it does differ, I
would suggest changing the name.

Cheers,
            Nat.

----- Original Message -----
From: "Clemens Hintze" <c.hintze@gmx.net>
Newsgroups: comp.lang.ruby
To: "ruby-talk ML" <ruby-talk@ruby-lang.org>; <undisclosed-recipients: ;>
Sent: Sunday, October 14, 2001 9:43 AM
Subject: [ruby-talk:22508] ANN: Generator -- a class supporting lazy
evaluation (Re: Open-ended ranges)


> Robert Feldt wrote:
>
> (...)
>
> > Ruby doesn't have infinite or unbounded data (by default) structs so
what
> > should this mean? We would have to add Inf (might be good for other
> > situations) and introduce Object#default_max_value, but how to handle
> >
> > (1..).to_a
> >
> > without going for lazy evaluation?
>
> (...)
>
> Robert,
>
> sorry for mis-using your post, but the opportunity is too nice to let
> it pass :-)
>
> There is a new class in town ... Generator. Generator is a class that
> supports you to execute associated code blocks only partially by
> suspending itself while returning an result to the caller.
>
>
> Suspending means, that the whole state of the code block will be
> stored in a
> Continuation instance. Next invocation of a Generator instance will
> back up where it
> was left previously, ready to compute and return another value when
> suspending again.
>
> Code could looks like this:
>
>
>    arr = ["Ruby", "Chan", "rules"]
>
>    igen = Generator.new { arr.each { |el| suspend el } }
>
>    puts igen.next      #-> Ruby
>
>    puts igen.next      #-> Chan
>
>    puts igen.next      #-> rules
>
>
> The more comprehensive documentation is stored together with the
> source code in RD format.
> Let me know, if you like this gimmick or, of course, if you find any
> errors!
>
> You may obtain it from RAA:
>
>    http://www.ruby-lang.org/en/raa-list.rhtml?name=Generator
>
>
> Much fun,
> \cle
>