Dear John, dear William,
On Feb 20, 11:45 pm, "William Stein" <[EMAIL PROTECTED]> wrote:
> On Wed, Feb 20, 2008 at 1:22 PM, John Palmieri <[EMAIL PROTECTED]> wrote:
>
> > By the way, is the following a bug?
>
> > sage: singular.LIB('ncall.lib')
> > sage: R=singular.ring(0,'(x1,x12,x2)','dp')
> > sage: C=singular.matrix(3,3,'1,-1,-1, -1,1,-1, -1,-1,1')
> > sage: C
>
> > 1, -1,-1,
> > -1,1, -1,
> > -1,-1,1
> > sage: R=singular.ring(0,'(x1,x12,x2)','dp')
> > sage: C
> > `sage1`
>
> > Calling singular.ring(...) seems to redefine C.
>
> > (I discovered this because when I was making a copy of the algebra S,
> > I wanted to use the same matrix C for the copy, but by that point it
> > had been redefined to be `sage1`, to my surprise.)
>
> No, it is not a bug. It's a perfect example of how
> Singular itself has a rather -- let's say old fashioned ...
... or neatly ordered...
The point is that a matrix in Singular has coefficients in a ring.
There may be different rings at the same time, but only one of them is
active (its nick name is "basering"). If you want to access a matrix
then you first have to make its ring active (using "setring").
Above, you define a ring, define a matrix in that ring, and then
change the ring (it doesn't matter that it is re-defined by an exact
copy of itself). So the matrix is lost.
Yours
Simon
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