From: Robert Klemme <bob.news@...>
Date: 2005-06-03T23:50:25+09:00
Subject: Re: internal iterators in ruby

Geert Fannes wrote:
> 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.

http://raa.ruby-lang.org/search.rhtml?search=iterator

Dunno about the internals though.

Kind regards

    robert

> 
> -----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