Function: quadunit
Section: number_theoretical
C-Name: quadunit0
Prototype: GDn
Help: quadunit(D,{v = 'w}): fundamental unit u of the quadratic field of
discriminant D where D must be positive.
If v is given, the variable name is used to display u, else 'w' is used.
Doc: fundamental unit\sidx{fundamental units} $u$ of the
real quadratic field $\Q(\sqrt D)$ where $D$ is the positive discriminant
of the field. If $D$ is not a fundamental discriminant, this probably gives
the fundamental unit of the corresponding order. $D$ must be an integer
congruent to 0 or 1 modulo 4, which is not a square; the result is a
quadratic number (see \secref{se:quadgen}).
If \var{v} is given, the variable name is used to display $u$
else 'w' is used.
Variant:
When \var{v} does not matter, the function
\fun{GEN}{quadunit}{GEN D} is also available.