[GiNaC-devel] csgn patch

[Vladimir Kisil]

		Dear all,

		Here is the full patch for the power property of csgn()
  function. Its effect can be seen in the following  ginsh output:

> csgn(x)^3;
csgn(x)
> csgn(x)^5;
csgn(x)
> csgn(x)^2;
csgn(x)^2
> csgn(x)^(2/5);
csgn(x)^(2/5)
> csgn(x)^(6/2);
csgn(x)
> csgn(x)^(-2);
csgn(x)^(-2)
> csgn(x)^(-3);
csgn(x)^(-3)
> csgn(x)^(-3/3);
csgn(x)^(-1)
> csgn(x)^(-3/2);
csgn(x)^(-3/2)

Best wishes,
	 Vladimir
-- 
Vladimir V. Kisil     email: kisilv at maths.leeds.ac.uk
--                      www: http://maths.leeds.ac.uk/~kisilv/

Index: ginac/inifcns.cpp
===================================================================
RCS file: /home/cvs/GiNaC/ginac/inifcns.cpp,v
retrieving revision 1.87
diff -u -r1.87 inifcns.cpp
--- ginac/inifcns.cpp	13 Mar 2006 14:21:47 -0000	1.87
+++ ginac/inifcns.cpp	13 Mar 2006 15:56:20 -0000
@@ -252,10 +252,23 @@
 	return csgn(arg);
 }
 
+static ex csgn_power(const ex & arg, const ex & exp)
+{
+	if (is_a<numeric>(exp) && exp.info(info_flags::positive) && ex_to<numeric>(exp).is_integer()) {
+		if (ex_to<numeric>(exp).is_odd())
+			return csgn(arg);
+		else
+			return power(csgn(arg), _ex2).hold();
+	} else
+		return power(csgn(arg), exp).hold();
+}
+
+
 REGISTER_FUNCTION(csgn, eval_func(csgn_eval).
                         evalf_func(csgn_evalf).
                         series_func(csgn_series).
-                        conjugate_func(csgn_conjugate));
+                        conjugate_func(csgn_conjugate).
+                        power_func(csgn_power));
 
 
 //////////