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D.6.15.4 is_active
Procedure from library sing.lib (see sing_lib).
- Usage:
- is_active(f,id); f poly, id ideal or module
- Return:
- 1 if f is an active element modulo id (i.e. dim(id)=dim(id+f*R^n)+1,
if id is a submodule of R^n) resp. 0 if f is not active.
The basering may be a quotient ring
- Note:
- regular parameters are active but not vice versa (id may have embedded
components). proc is_reg tests whether f is a regular parameter
Example:
| | LIB "sing.lib";
ring r =32003,(x,y,z),ds;
ideal i = yx3+y,yz3+y3z;
poly f = x;
is_active(f,i);
==> 1
qring q = std(x4y5);
poly f = x;
module m = [yx3+x,yx3+y3x];
is_active(f,m);
==> 0
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