CoCoA » CoCoA-5

Reading Emanuela Napoli's master's thesis I came across the following example:

>>> j := [z^2, y^2*z +y*z, x*z +y*z, y^4 +2*y^3, x*y^2 +y^3 +x*y +y^2, x^2 +2*x*y +y^2, x^2 -2*x, y^2 +2*y, z];

>>> interreduced(j);
[z, y^2 +2*y, x^2 +2*x*y -2*y, -2*x*y -2*x +2*y, x +y]

>>> interreduced(It);
[z, x +y, y^2 +2*y]

I did not expect that applying interreduce twice would give a different answer.

Is this correct? If so, we should point it out in the manual.