Dear GAP Forum,
A user has reported a serious bug in the code for polynomial
reduction (thus also affecting Groebner bases), which may return
wrong results without warning. (See below for an example)
This bug will be corrected in the forthcoming next bugfix.
If you are using Groebner bases and need a temporary workaround
already now, you can
download the file
http://www.math.colostate.edu/~hulpke/workaround.gi
Read this file in with *Reread* (not Read, as it overwrites some
library functions)
We apologize for this problem!
Alexander Hulpke
Example with correct output:
x:=X(Rationals,"x");;
y:=X(Rationals,"y");;
a:=X(Rationals,"a");;
c:=X(Rationals,"c");;
s:=X(Rationals,"s");;
L:=[(a+c)*s-x,(a+c)*c-y,s^2+c^2-1];;
ReducedGroebnerBasis(L,MonomialLexOrdering([x,y,a,c,s]));
[ c^2+s^2-1, -a*c+s^2+y-1, -a*s-c*s+x ]
(2nd polynomial was wrong!)
-- Colorado State University, Department of Mathematics,
Weber Building, 1874 Campus Delivery, Fort Collins, CO 80523-1874, USA
email: [EMAIL PROTECTED], Phone: ++1-970-4914288
http://www.math.colostate.edu/~hulpke
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