"y \= scalar" fails

[Jaroslav Hajek]

On Mon, Mar 3, 2008 at 5:05 PM, Rolf Fabian <Rolf.Fabian at gmx.de> wrote:
>
>
>  Jaroslav Hajek-2 wrote:
>  >
>  > On Mon, Mar 3, 2008 at 1:42 PM, Rolf Fabian <Rolf.Fabian at gmx.de> wrote:
>  >>  Jaroslav Hajek-2 wrote:
>  >>  >
>  >>  > this seems 100% correct.
>  >>  > y \= c means y = y \ c = inv(y) * c,
>  >>  >
>  >>
>  >>  Thanks for explaining me, what a backslash
>  >>  division is supposed to do.
>  >
>  > Unfortunately, I didn't. The inv(y)*c thinkg was a mistake; it does
>  > not work that way.
>  > y \= c is indeed equivalent to y = y\c, the rest is not true.
>  > "Supposed to" is the problem here. Supposed by whom?
>  >
>  > --
>
> > RNDr. Jaroslav Hajek
>  > computing expert
>  > Aeronautical Research and Test Institute (VZLU)
>  > Prague, Czech Republic
>  > url: www.highegg.matfyz.cz
>  >
>
>  Did I write "how a backslash division is supposed to work"
>  or did I actually specify "what a backslash division is supposed
>  to do" ? You should better recognize the difference.
>

Either way, the question is the same. Supposed by whom? You, presumably.

>
>  The fact, that for an (invertible) square matrix y and scalar c
>  the command "y \= c" results in a size conflict error looks weird and
>  obscure to me. Moreover, the fact that MatLab behaves in the same
>  way does  not all all make this 'feature' less strange and less obscure.
>  The way how the calculation is actually done does not play
>  any role concerning that statement.
>
>  Again:
>  In my eyes, having to specify
>
>  "y \= c * eye( size (y))"
>  (for square y and constant c)
>
>  instead of "y \= c"
>
>  to get something which is 'conceptually identical'
>  to "y \= c"
>
>  is extremely ugly and needs to be improved
>  by allowing syntax "y \= c" for that special
>  case.
>
>

OK, no problem. In my eyes, matrix \=  scalar is confusing. Perhaps
just because I've never seen it (because it does not work). Anyway, I
think such an extension would be easy to implement. I'd even volunteer
to do it if more people are interested.
Does anyone else share Rolf's opinion?

regards,
-- 
RNDr. Jaroslav Hajek
computing expert
Aeronautical Research and Test Institute (VZLU)
Prague, Czech Republic
url: www.highegg.matfyz.cz