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D.2.4.7 Prep

Procedure from library grobcov.lib (see grobcov_lib).

Usage:
Prep(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 P-representation of the locally closed set V(N) - V(M) Output: [Comp_1, .. , Comp_s ] where
Comp_i=[p_i,[p_i1,..,p_is_i]]
KEYWORDS: locally closed set; canoncial form
EXAMPLE: Prep; 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-1;
Prep(p,q);
==> [1]:
==>    [1]:
==>       _[1]=b
==>    [2]:
==>       [1]:
==>          _[1]=1
==> [2]:
==>    [1]:
==>       _[1]=a
==>    [2]:
==>       [1]:
==>          _[1]=b-1
==>          _[2]=a