primelt.spad line 101 [edit on github]
FunctionsSpacePrimitiveElement provides functions to compute primitive elements in functions spaces.
primitiveElement(a1, a2) returns [a, q1, q2, q] such that k(a1, a2) = k(a), , and ai = qi(a)q(a) = 0. The minimal polynomial for a2 may involve a1, but the minimal polynomial for a1 may not involve a2; This operations uses resultant.
primitiveElement([a1, ..., an]) returns [a, [q1, ..., qn], q] such that then k(a1, ..., an) = k(a), , and ai = qi(a)q(a) = 0. This operation uses the technique of Groebner basis.