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D.6.20.11 nf_icis
Procedure from library sing.lib (see sing_lib).
- Usage:
- nf_icis(i); i ideal
- Return:
- ideal = generic linear combination of generators of i if i is an ICIS
(isolated complete intersection singularity), return i if not
- Note:
- this proc is useful in connection with proc milnor
printlevel >=0: display comments (default)
Example:
| | LIB "sing.lib";
int p = printlevel;
printlevel = 1;
ring r = 32003,(x,y,z),ds;
ideal i = x3+y4,z4+yx;
nf_icis(i);
==> // complete intersection of dim 1
==> // dim-sequence:
==> // dim of singular locus = 0
==> // isolated singularity if last number is 0 in dim-sequence:
==> // dim of singular locus = 0
==> // isolated singularity if last number is 0 in dim-sequence:
==> // ICIS in generic form after 1 genericity loop(s)
==> _[1]=2xy+x3+y4+2z4
==> _[2]=xy+z4
ideal j = x3+y4,xy,yz;
nf_icis(j);
==> // no complete intersection
==> // dim-sequence:
==> // no complete intersection
==> _[1]=x3+y4
==> _[2]=xy
==> _[3]=yz
printlevel = p;
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