Function: alghasse
Section: algebras
C-Name: alghasse
Prototype: GDG
Help: alghasse(al,{pl}): the hasse invariant of the central simple algebra al at
 the place pl.
Doc: Given a central simple algebra \var{al} output by \tet{alginit} and a prime
 ideal or an integer between $1$ and $r_{1}+r_{2}$, returns a \typ{FRAC} $h$ : the
 local Hasse invariant of \var{al} at the place specified by \var{pl}.
 If \var{al} is an algebra over $\R$, returns the Hasse invariant of \var{al}
 \bprog
 ? nf = nfinit(y^2-5);
 ? A = alginit(nf, [-1,y]);
 ? alghasse(A, 1)
 %3 = 1/2
 ? alghasse(A, 2)
 %4 = 0
 ? alghasse(A, idealprimedec(nf,2)[1])
 %5 = 1/2
 ? alghasse(A, idealprimedec(nf,5)[1])
 %6 = 0
 ? H = alginit(1.,1/2); \\ Hamilton quaternion algebra
 ? alghasse(H)
 %8 = 1/2
 @eprog
