Function: rnfidealabstorel
Section: number_fields
C-Name: rnfidealabstorel
Prototype: GG
Help: rnfidealabstorel(rnf,x): transforms the ideal x from absolute to
 relative representation.
Doc: let $\var{rnf}$ be a relative
 number field extension $L/K$ as output by \kbd{rnfinit}, and $x$ an ideal of
 the absolute extension $L/\Q$ given by a $\Z$-basis of elements of $L$.
 Returns the relative pseudo-matrix in HNF giving the ideal $x$ considered as
 an ideal of the relative extension $L/K$.

 If $x$ is an ideal in HNF form, associated to an \var{nf} structure, for
 instance as output by $\tet{idealhnf}(\var{nf},\dots)$,
 use \kbd{rnfidealabstorel(rnf, nf.zk * x)} to convert it to a relative ideal.
