Dear William,

On Feb 20, 9:47 pm, "William Stein" <[EMAIL PROTECTED]> wrote:
> On Feb 20, 2008 12:30 PM, Simon King <[EMAIL PROTECTED]> wrote:
<snip>
> > Would it be a reasonable idea to implement such method, so that
> >  copy(R)
> > yields a ring that is isomorphic with R but has different variable
> > names (e.g., by adding a prime to the variable names)?
>
> No, that would not be reasonable. [[woah, John Palmieri just appeared
> in my office... chat for a while...] Anyway,copyshould return an 
> exactcopysince that's the semantics of __copy__ in Python.
<snip>
> > More generally, i believe it'd be a good idea to have a __copy__
> > method for *any* Sage objects defined via the Singular interface.
>
> > E.g., when one defines a matrix
> > sage: D=singular.matrix(3,3,'a,b,c, a**2,b**2,c**2, a**3,b**3,c**3')
> > then
> >   C=copy(D)
> > should be a copy of D (in the same ring). Up to now, one obtains
> > sage: C=copy(D)
> > sage: C
> > (invalid object -- defined in terms of closed session)
>
> I would certainly be all for that too!
>
> Any chance you could write it, or do I have to?

Done - see http://trac.sagemath.org/sage_trac/ticket/2300
With that patch, copy(R) for a SingularElement R returns a
SingularElement that is the same as R but not identical with R.

I am not sure whether that ticket belongs to "commutative algebra" or
to "interfaces". I chose "commutative algebra", hoping it is ok.

Cheers
     Simon
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