bug in raising a Series to a power

*To*: mathgroup at yoda.ncsa.uiuc.edu*Subject*: bug in raising a Series to a power*From*: dabell at ruflie.umd.edu (Dan Abell)*Date*: Fri, 1 Feb 91 13:45:48 EST

In raising a polynomial Series of more than one variable to some power, Mathematica responds with a rational Series. (!?) The following commands (Mathematica's response not shown) illustrate the problem. Here is a polynomial: poly[q_,p_] = Expand[ q+p + (q+p)^3 + (q+p)^5 ] Now turn this into a polynomial Series, keeping terms through order 6 in the variables q and p: poly[eps q, eps p] + O[eps]^7 Now try squaring this Series: ExpandAll[ (poly[eps q, eps p] + O[eps]^7)^2 ] Mathematica responds with a Series that includes rational sub-expressions. What's going on?