From: Randy Kramer <rhkramer@...>
Date: 2008-09-20T10:00:24+09:00
Subject: Re: why one array continues to grow after repeated call

On Friday 19 September 2008 03:19 pm, Brian Candler wrote:
> Here's a case where it does:
> 
>   # version 1
>   data = []
>   10.times { |i| data[i] = "hello" }
>   data[0] << "x"
>   p data
> 
>   # version 2
>   str = "hello"
>   data = []
>   10.times { |i| data[i] = str }
>   data[0] << "x"
>   p data

Wow!  That's either amazing or frightening (or both).  

I did use:

 10.times { |i| puts data[i].object_id}

... to see the object_id of each element in the arrays both above and 
below.

(For the record, version 1 creates 10 different objects, version 2 
creates only a single object.)

> 
> It does catch people out when they write, e.g.
> 
>   a = Array.new(10, [])
> 
> when what they really want is
> 
>   a = Array.new(10) { [] }
> 
> Try both these examples, printing out the object_id of each of the 10 
> elements of the array, to see how they are different.

Thanks again (I think ;-)

Randy Kramer
-- 
I didn't have time to write a short letter, so I created a video 
instead.--with apologies to Cicero, et.al.