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D.5.9.5 discr

Procedure from library spcurve.lib (see spcurve_lib).

Usage:
discr(sem,n); sem ideal, n integer

Assume:
sem is the versal deformation of an ideal of codimension 2.
the first n variables of the ring are treated as variables all the others as parameters

Return:
ideal describing the discriminant

Note:
This is not a powerful algorithm!

Example:
 
LIB "spcurve.lib";
ring r=32003,(x(1),x(2),x(3)),ds;
ideal curve=x(1)*x(2),x(1)*x(3),x(2)*x(3);
matrix M=isCMcod2(curve);
list l=matrixT1(M,3);
def sem=semiCMcod2(l[1],std(l[2]));
basering;
==> //   characteristic : 32003
==> //   number of vars : 6
==> //        block   1 : ordering ds
==> //                  : names    x(1) x(2) x(3) 
==> //        block   2 : ordering dp
==> //                  : names    A(1) A(2) A(3) 
==> //        block   3 : ordering C
discr(sem,3);
==> _[1]=A(1)*A(2)*A(3)


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