From: "David A. Black" <dblack@...>
Date: 2005-10-11T21:35:44+09:00
Subject: Re: multi-dimensional Arrays

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Hi --

On Tue, 11 Oct 2005, Peter v. N. wrote:

> Hi all,
>
> I'm a Ruby noob so please forgive me...

Welcome to Ruby!

> I know there exist "simple" ways (Google's thy friend)
> to create md arrays with Ruby. But it's somehow cumbersome
> and it would be nice if it could be done like "array =3D Array.new(3,3)" =
-> I=20
> know too that this means not the same in Ruby...
>
> What I like to know: what led to the decission to do it that way
> and not like it is done in the C/C++ (Java) languages =E0 la
> "int[][] arr =3D new int[3][3]"?
>
> Maybe because this approach is not strictly oo-oriented? But then,
> switches and loops in Ruby are neither.

OK... but finding a couple of things that aren't strictly OO doesn't
mean that Ruby should just give up and make everything non-OO :-)
Each part of Ruby is carefully designed to contribute to the whole
system.

In the case of int[][] arr... Ruby variables are always untyped.  If
you can do:

   arr =3D []

you can also do:

   arr =3D "I am not an array!"

The identifier 'arr' has no particular type.  That's a big part of the
dynamics and dynamism of Ruby.

Also, you're assuming that [] means "array indexing".  Actually, this:

   x[]

is just syntactic sugar for this:

   x.[]  # call method "[]"

and you can define [] to do whatever you want:

   obj =3D Object.new

   # Define a "singleton" method [] for obj
   def obj.[](x)
     "Are you trying to access index #{x}??"
   end

   puts obj[3] # Are you trying to access index 3??

So there's no reason to think that the notation [][] would mean
"nested array".

There's a Matrix class, by the way, that might help you automate what
you need to do a little more.


David

--=20
David A. Black
dblack@wobblini.net
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