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D.2.4.6 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]]
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;
// P-representation of V(p) \ V(q)
Prep(p,q);
==> [1]:
==> [1]:
==> _[1]=b
==> [2]:
==> [1]:
==> _[1]=1
==> [2]:
==> [1]:
==> _[1]=a
==> [2]:
==> [1]:
==> _[1]=b-1
==> _[2]=a
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