A discrete monomial valuation v on R=K[X
1,...,X
n] is determined by the values v(X
j) of the indeterminates. This function computes the subalgebra S={f∈R: v
i(f)≥0, i=1,...,n} for several such valuations v
i, i=1,...,r. The function needs the matrix V=(v
i(X
j)) as its input.
i1 : R=QQ[x,y,z,w];
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i2 : V0=matrix({{0,1,2,3},{-1,1,2,1}});
2 4
o2 : Matrix ZZ <--- ZZ
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i3 : valRing(V0,R)
2
o3 = ideal (y, x*y, w, x*w, z, x*z, x z)
o3 : Ideal of R
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