From: Dave Baldwin <dave.baldwin@3dlabs.com>
Date: 2008-10-10T02:00:12+09:00
Subject: Re: Bug in Vector class?


On 9 Oct 2008, at 16:13, Thomas B. wrote:

> Dave Baldwin wrote:
>> because the Vector#* method promotes self to a column vector when the
>> argument is found to be a Matrix.  I think it should be promoting  
>> self
>> to a row vector and making this change removes the exception and  
>> gives
>> the correct result.
>
> I think it should not. Either the programmer knows what he or she is
> doing and is able to take care of the matrices dimensions, or no magic
> auto-transpositions or other tricks are going to save their project  
> from
> falling apart sooner or later. Vector is a column vector, and let it  
> be
> this way.


The Vector class doesn't seem to have any idea that it is representing  
a row or column vector and as the class stands now a vector * matrix  
will always fail.

The only way to achieve this operation is to manually convert the  
vector into a Matrix with one row but now you are really doing a  
matrix * matrix operation and not using the failing path in Vector.

If the intent was for vector * matrix to fail then it would be better  
to raise an exception directly rather than rely on the Matrix class to  
catch a dimensional error.

I still think it is better to treat it as a row vector in this case.

Dave.

>
>
> TPR.
> -- 
> Posted via http://www.ruby-forum.com/.
>