CoCoA » CoCoALib

I had implemented a trick which I believed would be enough for interreducing (compute the GB twice).
But it is not (see #1379): indeed it is not even minimal (with lex).

Use QQ[x,y,z], Lex;
I := ideal(y*z -2*z^5 -2*z^4 +2*z^3,  y^2 -16*z^5 -12*z^4 +12*z^3 +12*z^2,  x*y -2*x*z -5*y +6*z^5 +2*z^3 -8*z^2 +10*z,  x^2 +10*x*z -10*x -51*z^5 +74*z^4 +16*z^3 -14*z^2 -50*z +25,  x*z^2 -x*z +5*z^5 -6*z^4 -4*z^3 +5*z,  z^6 -z^5 -z^4 +z^2,  z^3 -z -1);
GBasisByHomog(I);
-->  [y -4*z -2,  x -z^2,  x*z -z -1,  x^2 -z^2 -z,  z^3 -z -1]

The trick didn't work ... they usually don't.
Fixed interreduction

checked-in. Made new pre-release for Mac.

This works fine now, but only for few orderings.
The general case will not be done for this release. Postponing.

Urgent: DegLex (should be easy)