#### D.2.4.6 Prep

Procedure from library `grobcov.lib` (see grobcov_lib).

Usage:
  Prep(N,M);
  Input: ideal N (null ideal) (not necessarily radical nor maximal) ideal M (hole ideal) (not necessarily containing N)
  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]]
  NOTE: Operates in a ring R=Q[a] (a=parameters)
  KEYWORDS: Locally closed set, Canoncial form
  EXAMPLE: Prep; shows an example

Example:

    LIB "grobcov.lib";
    if(defined(Grobcov::@P)){kill Grobcov::@R; kill Grobcov::@P; kill Grobcov::@RP;}
    short=0;
    ring R=0,(x,y,z),lp;
    ideal E=x*(x^2+y^2+z^2-25);
    ideal N=x*(x-3),y-4;
    Prep(E,N);
    ==> [1]:
    ==>    [1]:
    ==>       _[1]=x2+y2+z2-25
    ==>    [2]:
    ==>       [1]:
    ==>          _[1]=z
    ==>          _[2]=y-4
    ==>          _[3]=x-3
    ==>       [2]:
    ==>          _[1]=z-3
    ==>          _[2]=y-4
    ==>          _[3]=x
    ==>       [3]:
    ==>          _[1]=z+3
    ==>          _[2]=y-4
    ==>          _[3]=x
    ==> [2]:
    ==>    [1]:
    ==>       _[1]=x
    ==>    [2]:
    ==>       [1]:
    ==>          _[1]=y-4
    ==>          _[2]=x

User manual for Singular version 4-0-3, 2016, generated by texi2html.