Improve diff(abs(x)) for real x.

diff --git a/ginac/inifcns.cpp b/ginac/inifcns.cpp
index d68afbb50df6d6f965e8d6bbbd4573cd9bdf5115..ec74a435de0774290f6d95baa221690b87420de7 100644 (file)
--- a/ginac/inifcns.cpp
+++ b/ginac/inifcns.cpp
@@ -321,6 +321,8 @@ static ex abs_expand(const ex & arg, unsigned options)
 static ex abs_expl_derivative(const ex & arg, const symbol & s)
 {
        ex diff_arg = arg.diff(s);
+       if (arg.info(info_flags::real))
+               return diff_arg*(2*step(arg) - 1);
        return (diff_arg*arg.conjugate()+arg*diff_arg.conjugate())/2/abs(arg);
 }