Function: polcoef
Section: polynomials
C-Name: polcoef
Prototype: GLDn
Help: polcoef(x,n,{v}): coefficient of degree n of x. With respect
 to the main variable if v is omitted, with respect to the variable v
 otherwise.
Description:
 (pol, 0):gen:copy       constant_coeff($1)
 (pol, 0,):gen:copy      constant_coeff($1)
 (pol, small):gen:copy   RgX_coeff($1, $2)
 (pol, small,):gen:copy  RgX_coeff($1, $2)
 (gen, small, ?var):gen  polcoeff0($1, $2, $3)
Doc: coefficient of degree $n$ of the polynomial $x$, with respect to the
 main variable if $v$ is omitted, with respect to $v$ otherwise.  If $n$
 is greater than the degree, the result is zero.

 Naturally applies to scalars (polynomial of degree $0$), as well as to
 rational functions whose denominator is a monomial. It also applies to power
 series: if $n$ is less than the valuation, the result is zero. If it is
 greater than the largest significant degree, then an error message is issued.
