From: "David A. Black" <dblack@...>
Date: 2005-10-12T08:13:11+09:00
Subject: Re: multi-dimensional Arrays

Hi --

On Wed, 12 Oct 2005, Peter v. N. wrote:

> Thank you for all the replies! This is really great.
>
> But I still wonder (or play dumb here):
>
> what's the difference between
>
> arr = Array.new(3) { Array.new(3) }
>
> 	and
>
> arr = Array.new(3, Array.new(3))

In the first one, the block is executed once each time to fill up the
array.  It's like:

   arr = [Array.new(3),Array.new(3),Array.new(3)]

So it's an array of three different arrays.

The second one sets all three initial values to the *same* array.
It's like:

   inner = Array.new(3)
   arr = [inner,inner,inner]

So you've got an array of three copies of the same object, which of
course has major implications when you modify that object, etc.


David

-- 
David A. Black
dblack@wobblini.net