On Thursday 03 September 2009, William Stein wrote:
> Hi Martin (and Sage-devel),
>
> I discovered that polynomial substitution is badly inconsistent between the
> symbolic ring and multivariate polynomials:
>
> sage: R. = QQ[]
> sage: f = x + 2*y
> sage: f.subs(x=y,y=x)
> 3*y
> sage: var('x,y')
>
I forwarded it to our team list.
I suppose, that your homomorphism uses Singulars map internally.
That should be a good solution for more than two parallel
substitutions.
Michael
On 3 Sep., 08:18, William Stein wrote:
> Hi Martin (and Sage-devel),
>
> I discovered that polynomial substitution is
