From: William Morgan <wmorgan-ruby-talk@...>
Date: 2004-08-27T05:42:05+09:00
Subject: Re: python generators to ruby closures, help

Excerpts (reformatted) from zuzu's mail of 26 Aug 2004 (EDT):
> http://www.ruby-doc.org/stdlib/libdoc/generator/rdoc/classes/Generator.html
> 
> am i correct in assuming that "makes an internal iterator external" is
> just another way of saying "turns a subroutine into a continuation",
> "using yield rather than return"?  or aka, a function to continuation
> translator?

I don't think that's right.T he goal of Generator is something much more
specific: to turn an internal iterator, i.e. a method that takes a block
argument, into an external iterator, i.e. an object with explicit #next?
and #next methods.

Think about trying to interlace two Enumerables, e.g. turn ["a","b","c"]
and [1,2,3] into ["a",1,"b",2,"c",3].  You can't use Enumerable#each (an
internal iterator) to do this in a natural way. Instead, you'd use
Generator to create an object for each Enumerable and explicitly have a
loop that called #next alternately on both objects.

Ruby's internal iterators are far, far friendlier to use than, say,
Java's external iterators (writing for loops really is a pain) but there
are some problems they just don't yield (hah hah) natural solutions to.

Sorry if that isn't what you were asking. I don't know whether this is
related to Python's "generator" objects at all.

-- 
William <wmorgan-ruby-talk@masanjin.net>