Function: sign
Section: operators
C-Name: gsigne
Prototype: iG
Help: sign(x): sign of x, of type integer, real or fraction.
Description:
 (mp):small          signe($1)
 (gen):small        gsigne($1)
Doc: \idx{sign} ($0$, $1$ or $-1$) of $x$, which must be of
 type integer, real or fraction; \typ{QUAD} with positive discriminants and
 \typ{INFINITY} are also supported.
