[GiNaC-devel] Bug in differentiation of power.

[Chris Dams]

Dear all,

I found out that when differentiating a power it is tested whether the 
exponent is real. If this is the case, code is executed that assumes that 
this exponent is a numeric. Hower, because we also have real symbols 
nowadays this is not correct. Besides, why would differentiating x^I need 
a special case? Its derivative is simply I*x^(I-1). Therefore, I changed 
this test into a check whether the exponent is a numeric.

I will also backport this change to 1.3.

Best,
Chris