Re: [Maxima-discuss] Matrix multiplication surprise and question

[Robert D. <rob...@gm...>]

On 2016-08-28, David Billinghurst <dbm...@gm...> wrote:

> (%i2) A: matrix([a11,a12],[a21,a22]);

> (%i4) r:matrix([1,0]);

> (%i6) A.r;
>                                      [ a11 ]
> (%o6)                               [     ]
>                                     [ a21 ]

There is code in MULTIPLYMATRICES to multiply by the transpose when the
second argument has one row. I suppose the rationale is that allows
multiplying A.foo where foo is a list instead of a matrix, and I guess
that's OK. But I think it's a bug to do the same for a matrix with one
row. See src/matrix.lisp circa line 483.

I think that stuff should be cut out of MULTIPLYMATRICES, and any
callers should ensure that the arguments are conformant (mungeing a list
argument as necessary).

FWIW

Robert Dodier