# [GiNaC-list] Skip my previous answer (WAS: Re: 1by1 matrix to scalar)

jros jros at unavarra.es
Wed Jun 23 15:50:40 CEST 2010

```Skip my previous answer, I didn't read the question
carefully.

Javier

On Wed, 2010-06-23 at 08:25 -0400, jros wrote:
> This is trivial from the GiNaC tutorial: I suppose you know
>
> Javier
>
>
> On Wed, 2010-06-23 at 13:19 +0200, Felipe Bordeu wrote:
> > any ideas ?
> >
> > Thanks.
> >
> > On 18/06/2010 15:06, Felipe Bordeu wrote:
> > > Hello,
> > >
> > > I have a little problem, I'm dealing functions made of matrix products.
> > >
> > > My question is, how can "force"  ginac to convert automatically all
> > > the 1by1 matrices to scalars?.
> > > or do I have to do it manually??
> > >
> > > Here is a simple example.
> > >
> > > void main2(){
> > >   ex m1=symbolic_matrix(1, 3, "x");
> > >   ex m2=symbolic_matrix(3, 1, "y");
> > >
> > >   cout <<  m1 << std::endl;
> > >   cout <<  m2 << std::endl;
> > >   ex m3 = (m1*m2).evalm();
> > >   cout << m3 << std::endl;
> > >   cout << ex_to<matrix>(m3)(0,0)<< std::endl;;
> > >   ex m4 = m3-ex_to<matrix>(m3)(0,0);
> > >   cout << m4 << std::endl;
> > > };
> > > the output :
> > >
> > > [[x0,x1,x2]]
> > > [[y0],[y1],[y2]]
> > > [[y1*x1+y2*x2+y0*x0]]
> > > y1*x1+y2*x2+y0*x0
> > > -y1*x1+[[y1*x1+y2*x2+y0*x0]]-y2*x2-y0*x0
> > >
> > > the last line "should" be zero ?--
> > >
> > > thanks
> > >
> > > Felipe
> > >
> > > _______________________________________________
> > > GiNaC-list mailing list
> > > GiNaC-list at ginac.de
> > > https://www.cebix.net/mailman/listinfo/ginac-list
> >
> >

```