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D.15.17.1 LTGS
Procedure from library sagbigrob.lib (see sagbigrob_lib).
- Usage:
- LTGS(I,A); I ideal of subalgebra A, A subalgebra (which is a finite sagbi basis).
- Return:
- a module M.
Example:
| | LIB "sagbigrob.lib";
// Example 1:
ring r=ZZ,(x,y),Dp;
ideal A=2x2+xy,2y2,3xy;
ideal I=4x2y2+2xy3,18x2y4,36xy5;
LTGS(I,A);
==> _[1]=9y2*gen(1)-2*gen(2)
==> _[2]=9y4*gen(1)-xy*gen(3)
==> _[3]=-xy*gen(3)+2y2*gen(2)
==> _[4]=xy3*gen(1)
==> _[5]=-18xy3*gen(1)+2x2*gen(3)+xy*gen(3)
// Example 2:
ring r2=QQ,(x,y),Dp;
ideal A=x2,xy;
ideal I=x3y+x2,x4+x2y2,-x3y3-x2y2;
LTGS(I,A);
==> _[1]=x2*gen(1)-xy*gen(2)
==> _[2]=-x2y2*gen(1)-x2*gen(3)
==> _[3]=-x3y3*gen(2)-x4*gen(3)
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