[PATCH 1/3] Automatic evaluation of (e^t)^s = e^(ts).

[ginac.git] / ginac / inifcns_trans.cpp

diff --git a/ginac/inifcns_trans.cpp b/ginac/inifcns_trans.cpp
index 49e30047f9f78485e84ff4d3650dfd737bc59ef9..f6550f6d734ba7e4dfa1798d6de3cee6595e05fb 100644 (file)
--- a/ginac/inifcns_trans.cpp
+++ b/ginac/inifcns_trans.cpp
@@ -128,6 +128,24 @@ static ex exp_conjugate(const ex & x)
        return exp(x.conjugate());
 }
 
+static ex exp_power(const ex & x, const ex & a)
+{
+       /*
+        * The power law (e^x)^a=e^(x*a) is used in two cases:
+        * a) a is an integer and x may be complex;
+        * b) both x and a are reals.
+        * Negative a is excluded to keep automatic simplifications like exp(x)/exp(x)=1.
+        */
+       if (a.info(info_flags::nonnegative)
+           && (a.info(info_flags::integer) || (x.info(info_flags::real) && a.info(info_flags::real))))
+               return exp(x*a);
+       else if (a.info(info_flags::negative)
+                && (a.info(info_flags::integer) || (x.info(info_flags::real) && a.info(info_flags::real))))
+               return power(exp(-x*a), _ex_1).hold();
+
+       return power(exp(x), a).hold();
+}
+
 REGISTER_FUNCTION(exp, eval_func(exp_eval).
                        evalf_func(exp_evalf).
                        expand_func(exp_expand).
@@ -135,6 +153,7 @@ REGISTER_FUNCTION(exp, eval_func(exp_eval).
                        real_part_func(exp_real_part).
                        imag_part_func(exp_imag_part).
                        conjugate_func(exp_conjugate).
+                       power_func(exp_power).
                        latex_name("\\exp"));
 
 //////////