From: Jonathan Leighton <lists@...>
Date: 2006-01-30T00:33:29+09:00
Subject: Re: Loop weirdness

On Sun, 2006-01-29 at 23:35 +0900, dblack@wobblini.net wrote:
> Hi --
> 
> On Sun, 29 Jan 2006, Jonathan Leighton wrote:
> 
> > Okay, so let me get this right... if you do
> >
> > foo.each { }
> >
> > foo is re-evaluated with each iteration? Hence the bug? Why?
> 
> The length of foo is re-evaluated each time; that's how the decision
> is made whether or not to keep iterating.  Array#each essentially
> works like this:
> 
>    def each
>      i = 0
>      while i < length
>        yield self[i]
>        i += 1
>      end
>      self
>    end
> 
> So if the length of the array increases in mid-stream, the iteration
> will continue, based on the while test.
> 
> You can always get around this with something like:
> 
>    array.length.times do |i|
>      # do something with array[i]
>    end
> 
> where length won't be re-evaluated.

Thanks very much! I understand now.

-- 
Jonathan Leighton
http://turnipspatch.com/ | http://jonathanleighton.com/ | http://digital-proof.org/