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D.4.25.3 sagbiNF
Procedure from library sagbi.lib (see sagbi_lib).
- Usage:
- sagbiNF(id,dom,k[,n]); id either poly or ideal,dom ideal, k and n positive intergers.
- Return:
- same as type of id; ideal or polynomial.
| The integer k determines what kind of s-reduction is performed:
- if (k=0) no tail s-reduction is performed.
- if (k=1) tail s-reduction is performed.
Three Algorithm variants are used to perform subalgebra reduction.
The positive integer n determines which variant should be used.
n may take the values (0 or default),1 or 2.
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- Note:
- computation of subalgebra normal forms may be performed in polynomial rings or quotients
thereof
Example:
| LIB "sagbi.lib";
ring r=0,(x,y),dp;
ideal I= x2-xy;
qring Q=std(I);
ideal dom =x2,x2y+y,x3y2;
poly p=x4+x2y+y;
sagbiNF(p,dom,0);
==> 0
sagbiNF(p,dom,1);// tail subalgebra reduction is performed
==> 0
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