Re: Is ther any sense in *= and matrices?

["John R. Strohm" <strohm@airmail.net>]

"Preben Randhol" <randhol+abuse@pvv.org> wrote in message
news:slrnbduaav.6dd.randhol+abuse@kiuk0152.chembio.ntnu.no...
> Vinzent Hoefler wrote:
> > Preben Randhol wrote:
> >
> >>I mean even if one define "*" for Matrix_Type one cannot do:
> >>
> >>   A := A * B
> >
> > You can, iff A and B are square matrices.
>
> Yes, but that is a special case.

Not quite.

A[m x n] = B[m x p] * C[p x n]

You would want *= to work for a general result, which is

A[m x n] = A[m x n] * B[n x n]

If the matrices are not compatible for multiplication, then their product is
not mathematically defined, at all.

Usually, of course, you are only interested in square matrices.