From: Dave Thomas <Dave@...>
Date: 2000-12-14T15:45:27+09:00
Subject: [ruby-talk:7200] Re: Harmful preselection by yielding?

Aleksi Niemel� <aleksi.niemela@cinnober.com> writes:

> So, do you prefer to "fix in" the yielding instead of returning the
> produced data structure. And which is the criteria you base your
> decision on (feeling goes, but something more tangible would be
> great)?

If I hadn't been lazy, I'd have written

   def getpwent
     result = block_given? || []
     File.foreach("/etc/passwd") do |line|
       fields = line.split(/:/)
       if block_given?
         yield fields
       else
         result << fields
       end
     end
     return result
   end

And give the user the choice.

   getpwent { |login, pw, uid| puts "#{login}-#{uid}" }

or

   pwd = getpwent

In general, I find that I'm using iterator forms more and more. For
many applications, they tend to provide a natural flow to the
application. Of course, there'll often be times where it's more
convenient to have all the data lying around. So I guess the decision
comes down primarily to the data itself: is it inherently a
single-pass scan, or something that you'll be traversing many times.


And of course, in this particular case, I'd probably use the Etc
module as eban suggested and do it properly ;-)


Dave