From: Xavier Noria <fxn@...>
Date: 2008-09-21T07:50:50+09:00
Subject: Re: for or each?

On Sun, Sep 21, 2008 at 12:26 AM, Joe Wölfel <joe@talkhouse.com> wrote:
>                        for i in 0...(a.size)
>                                x += a[i]
>                        end

Hey that's not the for-version of #each, nobody iterates by index in
dynamic languages unless he needs to.

The message to the OP is: for versus each is a stylistic discussion in
the sense that they are equivalent *if used the way I showed*. A
regular loop over a collection using indexes is never used in dynamic
languages because it is much slower than array indexing in C. That's
the price you pay for such flexible estructures. In Ruby an array has
nothing to do behind the scenes with a C array.

That's why VHLLs provide specific efficient and concise collection iterators:

   # Perl
   foreach my $user (@users) {
       ...
   }

   # Ruby
   for user in users
     ...
   end

   # or

   users.each do |user|
     ...
   end

   # Python
   for user in users
       ...

   # Lisp
   (dolist (user users)
     (...))