From: Geert Fannes <Geert.Fannes@...>
Date: 2005-06-03T20:28:47+09:00
Subject: Re: internal iterators in ruby

Yes, indeed, something cursor-like. Enumerable#getCursor returns a
rewinded Cursor and Cursor#next provides the method to retrieve
subsequent elements. Does something like this already exist for Ruby?
Geert.

-----Original Message-----
From: Robert Klemme [mailto:bob.news@gmx.net] 
Sent: 03 June 2005 12:15
To: ruby-talk ML
Subject: Re: internal iterators in ruby

Geert Fannes wrote:
> So, if I understand well, the problem with iterating over different
> enumerables synchronously has to do with the absence of a #rewind and
> #next method for enumerables. The Generator class solves this using
> the slow #callcc method and allows one to step through the
> Enumerable#each method, element by element. Wouldn't it be better if
> the enumerable required a #rewind and #next method and constructs the
> #each method out of these instead of doing the reverse using #callcc?

No, this would not be better because then you would have to place
iteration state into the Enumerable which is at least ugly (it wastes
memory most of the time, i.e. the time when there is no iteration) and
it
doesn't allow for multiple concurrent iterations on the same instance.

A better alternative would be to encourage providers of Enumerables to
provide an external iterator for special cases.  This then will be more
efficient than callcc.

Kind regards

    robert