Feature #876
subst: allowed also for indets in the coeff ring
Description
Suppose we have a poly ring of the form QQ(a,b)[x,y]
and I want to substitute b=a+1
.
Currently subst
refuses because b
is not an indet of the ring.
Working around this is very cumbersome.
History
#1 Updated by John Abbott almost 8 years ago
Here is an example I was trying with Sandro Logar
QQa1 ::= QQ[a[1..6], alpha, beta]; QQa := NewFractionField(QQa1); P ::= QQa[x,y,z], lex; use P; conica := ScalarProduct(support((x+y+z)^2), [a[i] | i in 1..6]); cond1 := subst(conica, [[x,0], [y, 0], [z, 1]]); --a6 := num(LC(a[6])); -- GIVES ERROR !conica1 := subst(conica, a[6], 0); conica1 := sum(first(monomials(conica), 5)); retta := alpha*x + beta*y; retta; I := ideal(conica1, retta); RGB := ReducedGBasis(I); indent(RGB);