Function: qfbprimeform
Section: number_theoretical
C-Name: primeform
Prototype: GGp
Help: qfbprimeform(x,p): returns the prime form of discriminant x, whose
first coefficient is p.
Doc: prime binary quadratic form of discriminant
$x$ whose first coefficient is $p$, where $|p|$ is a prime number.
By abuse of notation,
$p = \pm 1$ is also valid and returns the unit form. Returns an
error if $x$ is not a quadratic residue mod $p$, or if $x < 0$ and $p < 0$.
(Negative definite \typ{QFI} are not implemented.) In the case where $x>0$,
the ``distance'' component of the form is set equal to zero according to the
current precision.