From: MonkeeSage <MonkeeSage@...>
Date: 2007-11-29T04:17:12+09:00
Subject: Re: Ruby needs continuations...

On Nov 28, 12:08 pm, "Eric I." <rubytrain...@gmail.com> wrote:
> On Nov 28, 7:29 am, "Just Another Victim of the Ambient Morality"
>
>
>
> <ihates...@hotmail.com> wrote:
> >     One weakness of Ruby iterators that continuations don't have is parallel
> > iteration.  If you have two containers that represent different aspects of
> > the same things, it's difficult to iterate over both of them in Ruby.  In
> > Python, you can do this:
>
> > list1 = [1, 2, 3, 4]
> > list2 = ['a', 'b', 'c', 'd']
>
> > # Okay, Python is more wordy than I'd like
> > # I could have just used zip() but you rarely need the list!
> > for num, letter in itertools.izip(list1, list2):
> >     # Do something with both numbers and letters
> >     print num, letter
> >     print
>
> >     How would one do this in Ruby?
>
> At RubyConf 2007 last month, Matz announced that 1.9 would have
> external iterators.  That would allow you to do this:
>
> num_iter = list1.each
> let_iter = list2.each
> loop {
>   puts num_iter.next, let_iter.next
>
> }
>
> When you reach the end of either list (or any list, if we scale beyond
> just two), the call to next would raise an exception, automatically
> caught by the loop construct, causing the loop to simply exit.  So
> this construct works gracefully even if one of the lists is shorter
> than the other(s).
>
> Eric
>
> P.S. I put together a very short presentation for the Southeast
> Michigan Ruby Users' Group summarizing what Matz said about 1.9.  You
> can see the slides at:
>
>    http://learnruby.com/ruby-1.9.html
>
> ====
>
> Are you interested in on-site Ruby training that uses well-designed,
> real-world, hands-on exercises?http://LearnRuby.com

Cool! I just tried that, and they're already in there (1.9.0
patchlevel 0). :)

Regards,
Jordan