From: Vincent Fourmond <vincent.fourmond@9online.fr>
Date: 2006-12-21T22:21:50+09:00
Subject: Re: Matrix class for ruby? -example

seepee wrote:
> On Thu, 21 Dec 2006 09:12:47 +0200, seepee wrote:
> 
>> Does anyone know of a functional Matrix math class for ruby that could
>> multiply, add and substract 3x2 or larger matrices.
>>
>> The matrix.rb that is in Ruby API cannot multiply anything larger than 2x2
>> matrices, which makes it useless for 2D or 3D graphics (for instance).
>>
>> SP
> 
> Problem:
> go to terminal, and type "irb" or "irb1.8"
> 
>> require 'matrix' #or require >rubylibrarypath/matrix.rb
>> p Matrix[ [25, 93, 33], [0, -1, 66] ] * Matrix[ [1, 53, 33], [1, -21, 77]

  Err... Have you done matrix computations for a long time ? You need
that the number of *columns* from the left matrix matches the number of
*lines* from the right matrix. If you try to multiply two 3x2 matrices,
it is rather encouraging that Matrix refuses it...

  Try transposing your matrix first, if that is what you need. Are you
dealing with transformation matrices (which are not real matrices) ?

	Vincent

-- 
Vincent Fourmond, PhD student
http://vincent.fourmond.neuf.fr/