From: Benoit Daloze <eregontp@...>
Date: 2010-05-13T22:07:18+09:00
Subject: Re: In Ruby, can the coerce() method know what operator it is th

Hi,
2010/5/13 Colin Bartlett <colinb2r@googlemail.com>:
> (B) The actual code in Matrix::Scalar#+ raises an exception for
> Numeric + (Matrix or Vector),
>
> but also allows for (Numeric or
> Matrix::Scalar) + Matrix::Scalar, with in both cases the result being
> Matrix::Scalar, and I can't immediately think of any circumstances
> where those cases would actually arise.

I first thought this would be for performance reason, to coerce once
instead of 2 times, but I don't see any use case except:
(Matrix::Scalar.new(4) + 3) * matrix
which should never be done, as Matrix::Scalar is supposed to be a private class:

  # Private CLASS
  class Scalar < Numeric # :nodoc:

Maybe Marc-André (the new maintainer) could give us a hint if he sees
this thread.

Personally, I used a simple Scalar class like in Matrix, but I just
define the * and / operator. Then if you do
Numeric + Matrix, you get:
NoMethodError: undefined method `+' for #<EMatrix::Scalar>
Which is almost self-explanatory I think.

Regards,
B.D.