Function: idealintersect
Section: number_fields
C-Name: idealintersect
Prototype: GGG
Help: idealintersect(nf,A,B): intersection of two ideals A and B in the
number field defined by nf.
Doc: intersection of the two ideals
$A$ and $B$ in the number field $\var{nf}$. The result is given in HNF.
\bprog
? nf = nfinit(x^2+1);
? idealintersect(nf, 2, x+1)
%2 =
[2 0]
[0 2]
@eprog
This function does not apply to general $\Z$-modules, e.g.~orders, since its
arguments are replaced by the ideals they generate. The following script
intersects $\Z$-modules $A$ and $B$ given by matrices of compatible
dimensions with integer coefficients:
\bprog
ZM_intersect(A,B) =
{ my(Ker = matkerint(concat(A,B)));
mathnf( A * Ker[1..#A,] )
}
@eprog