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D.2.4.6 Crep

Procedure from library grobcov.lib (see grobcov_lib).

Usage:
Crep(ideal N,ideal M);
ideal N (null ideal) (not necessarily radical nor maximal) in Q[a]. (a=parameters, x=variables). ideal M (hole ideal) (not necessarily containing N) in Q[a]. To be called in a ring Q[a][x] or a ring Q[a]. But the ideals can contain only the parameters in Q[a].

Return:
The canonical C-representation [P,Q] of the locally closed set, formed by a pair of radical ideals with P included in Q, representing the set V(P) - V(Q) = V(N) - V(M) KEYWORDS: locally closed set; canoncial form
EXAMPLE: Crep; shows an example

Example:
 
LIB "grobcov.lib";
short=0;
if(defined(R)){kill R;}
ring R=0,(a,b,c),lp;
ideal p=a*b;
ideal q=a,b-2;;
Crep(p,q);
==> [1]:
==>    _[1]=ab
==> [2]:
==>    _[1]=b-2
==>    _[2]=a