From: "Mauricio Fernández" <batsman.geo@...>
Date: 2005-04-20T17:30:18+09:00
Subject: Re: [PATCH] Trivial speedup in Array#zip

On Wed, Apr 20, 2005 at 11:12:55AM +0900, daz wrote:
> > On Wed, Apr 20, 2005 at 07:02:24AM +0900, Nobu wrote:
> > > `tmp' can be modified or stored anywhere while yielding, [...]
> >
> > I see. What about this?
> >
> > [snip "this"]
> 
> I guess Nobu's answer remains the same ?
[...] 
>   arr = []
>   [1,2,3].zip([4,5,6]){|x| arr.push(x) if x.include?(4)}
>   p arr  #-> [[1, 4]]
> 
> With your change (reusing 'tmp'), the stored reference in arr
> would dynamically change throughout the zip loop and the final
> (very incorrect) value in arr would be [[3, 6]].
> (Only one value was pushed by the code block, however, and it
> was the correct result at that time).

"this" should handle that correctly:

batsman@tux-chan:/tmp/ruby$ ./ruby
  arr = []
  [1,2,3].zip([4,5,6]){|x| arr.push(x) if x.include?(4)}
  p arr
[[1, 4]]
batsman@tux-chan:/tmp/ruby$ ruby
  arr = []
  [1,2,3].zip([4,5,6]){|x| arr.push(x) if x.include?(4)}
  p arr
[[1, 4]]


-- 
Mauricio Fern�ndez