D.5.8.3 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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&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; User manual for <a href="http://www.singular.uni-kl.de/"><i>Singular</i></a> version 2-0-4, October 2002,
generated by <a href="http://www.gnu.org/software/texinfo/"><i>texi2html</i></a>.
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