From: Xavier Noria <fxn@...>
Date: 2008-09-21T07:57:39+09:00
Subject: Re: for or each?

On Sun, Sep 21, 2008 at 12:52 AM, Phlip <phlip2005@gmail.com> wrote:
> Joe Wölfel wrote:
>
>> You can try my test if you like.  I haven't checked it carefully.   But it
>> does seem like 'each' is much faster under both ruby 1.86 and  ruby 1.9.
>>  The code is below.
>
> I just experimented with 'for' and found it does not reevaluate its header
> each time it runs. That's the only thing that could have explained the time
> difference, so maybe Matz & Co. have simply neglected 'for' while optimizing
> .each, which everyone uses. (Though it's still technically superior; not
> just an /ad populum/ thing...)
>
> Another reason to use .each is your collection-like class might override it
> to do something cool...

There's a technical difference in scopes between them, but for indeed
calls #each. A for loop

   for user in users
     ...
   end

assumes that users is whatever object that responds to #each, calls
the iterator on users and yields the value.