From: Paul Brannan <pbrannan@...>
Date: 2001-11-15T00:06:09+09:00
Subject: [ruby-talk:25187] Re: Parallel array iteration

One option is, of course, using an index to iterate over the array.
Another option is an "external iterator" that has at least two methods: 1)
get the current element, 2) advance to the next element.  There are a
number of implementations of external iterators out there;  some of them
convert the container to an array and then iterate over the array, while
others use a continuation to keep state while iterating.  There was some
discussion on the Rubygarden about knu's external iterators at:

  http://www.rubygarden.org/article.php?sid=107

Also be sure to read the FAQ at:

  http://www.rubycentral.com/faq/rubyfaq-5.html#ss5.5

Horst Duchene has written a set of external iterators that he calls
"streams":

  http://www.ruby-lang.org/en/raa-list.rhtml?name=stream.rb

My personal favorite is what I call a "buffered continuation iterator":

  http://rm-f.net/~cout/ruby/treasures/RubyTreasures-0.1/lib/iterator/buffered_continuation_iterator.rb

Paul

On Wed, 14 Nov 2001, Jim Freeze wrote:

> Hi
>
> I've got a block here...It seems that I have seen that
> Ruby can do iteration over multiple arrays, but I have
> not been able to find it. For example, I would like
> to do something like the following:
>
> a=%w{a b c}
> b=[1,2,3]
>
> for x,y in a,b
>  puts "#{x},#{y}"
> end
>
> a,1
> b,2
> c,3
>
>
> Or even better yet, do the above without the 'for'.
> Yes, I can do this with each_index, but I would like to avoid
> de-indexing if I don't have to.
>
> Thanks
>
>
>
> =========================================================
> Jim Freeze
> jim@freeze.org
> ---------------------------------------------------------
> Today is a fine day for Ruby programming.
> http://www.freeze.org
> =========================================================
>