ceil() bug?

[Michael Somos <somos@grail.cba.csuohio.edu>]

                    GP/PARI CALCULATOR Version 2.0.17 (beta)
gp> ceil(sum(n=-5,5,x^n))
%1 = x^5 + x^4 + x^3 + x^2 + x + 1
gp> ??ceil
ceil(x):

   ceiling  of x.   When x is in R,  the result is the smallest integer greater
than or equal to x.

   The library syntax is gceil(x).

Notice that the negative powers of x are removed. This behavior seems
not to be documented. Is this a bug? Shalom, Michael

-- 
Michael Somos <somos@grail.cba.csuohio.edu>     Cleveland State University
http://grail.cba.csuohio.edu/~somos/            Cleveland, Ohio, USA 44115