[GiNaC-devel] Powers of exponents

[Vladimir V. Kisil]

		Dear Richard,

>>>>> On Wed, 30 Sep 2009 23:39:25 +0200, "Richard B. Kreckel" <kreckel at ginac.de> said:

    RK> The rewriting rule pow(exp(x),a) -> exp(a*x) is not correct in
    RK> the general complex case. Consider a=1/2 and x=-I*Pi, for
    RK> instance. 

	Thanks for pointing out this. I am attaching a patch which do the
  substitution only for real x and a.

  Best wishes,
  Vladimir
-- 
Vladimir V. Kisil     email: kisilv at maths.leeds.ac.uk
--                      www: http://maths.leeds.ac.uk/~kisilv/
-------------- next part --------------
--- inifcns_trans.cpp	2009-02-17 13:39:22.000000000 +0000
+++ patches/inifcns_trans.cpp	2009-10-01 16:03:58.000000000 +0100
@@ -99,9 +99,18 @@
 	return exp(GiNaC::real_part(x))*sin(GiNaC::imag_part(x));
 }
 
+static ex exp_power(const ex & x, const ex & a)
+{
+	if (x.info(info_flags::real) && a.info(info_flags::real))
+		return exp(x*a);
+
+	return power(exp(x), a).hold();
+}
+
 REGISTER_FUNCTION(exp, eval_func(exp_eval).
                        evalf_func(exp_evalf).
                        derivative_func(exp_deriv).
+                       power_func(exp_power).
                        real_part_func(exp_real_part).
                        imag_part_func(exp_imag_part).
                        latex_name("\\exp"));