Function: ellrootno
Section: elliptic_curves
C-Name: ellrootno
Prototype: lGDG
Help: ellrootno(E,{p=1}): root number for the L-function of the elliptic
 curve E. p can be 1 (default), global root number, or a prime p (including
 0) for the local root number at p.
Doc:
 $E$ being a \var{smallell} as output by
 \kbd{ellinit}, this computes the local (if $p\neq 1$) or global (if $p=1$)
 root number of the L-series of the elliptic curve $E$. Note that the global
 root number is the sign of the functional equation and conjecturally is the
 parity of the rank of the \idx{Mordell-Weil group}. The equation for $E$ must
 have coefficients in $\Q$ but need \emph{not} be minimal.
