Function: nfeltmulmodpr
Section: number_fields
C-Name: nfmulmodpr
Prototype: GGGG
Help: nfeltmulmodpr(nf,x,y,pr): element x.y modulo pr in nf, where pr is in
 modpr format (see nfmodprinit).
Doc: given two elements $x$ and
 $y$ in \var{nf} and \var{pr} a prime ideal in \kbd{modpr} format (see
 \tet{nfmodprinit}), computes their product $x*y$ modulo the prime ideal
 \var{pr}.
Variant: This function is normally useless in library mode. Project your
 inputs to the residue field using \kbd{nf\_to\_Fq}, then work there.