From: Paul Lutus <nospam@...>
Date: 2006-09-11T12:00:23+09:00
Subject: Re: Matrix

Just Another Victim of the Ambient Morality wrote:

/ ...

>> You can only set an arbitrary element of a Matrix when it is created.
>> Once created, you can't change any of the entries.
> 
>     The []= operator does seem conspicuously missing.  If anyone knows why
> this was (obviously) deliberately left out, please say something!

Matrices are meant to be operated on as units, not by manipulating the
contents of individual cells. Think of a matrix as a datatype, a complete,
self-contained entity, one you can create or destroy in its entirety.

BTW, in answer to an earlier question:

> a) Is there a way to create a non-square matrix in ruby?

#! /usr/bin/ruby

require 'matrix'

m = Matrix[[1,2,3],[4,5,6],[7,8,9]]

nsqm = Matrix[[1,2,3],[7,8,9]]

puts m,nsqm

Matrix[[1, 2, 3], [4, 5, 6], [7, 8, 9]]
Matrix[[1, 2, 3], [7, 8, 9]]

> 
> Of course, if this is useful to you, you can always add it, yourself!
> I think it would go something like this...
> 
> 
> require 'matrix'
> 
> class Matrix # are for kids!
>     def []= (i, j, v)
>         @rows[i][j] = v
>     end
> end

Yes, this works as expected. Easy enough to add if you really want it. :)

-- 
Paul Lutus
http://www.arachnoid.com