From 2db113296f65f8fd3a0d62781ddc9276ff07b487 Mon Sep 17 00:00:00 2001
From: Christian Bauer <Christian.Bauer@uni-mainz.de>
Date: Mon, 20 Mar 2000 15:17:44 +0000
Subject: [PATCH 1/1] - fixed bug in normal(): normal(x^a) became (x^(-a))^(-1)
 - first shot at inert Diff() and Derivative() functions; still buggy!

---
 ginac/function.pl     |  8 ++++++--
 ginac/inifcns.cpp     | 41 +++++++++++++++++++++++++++++++++++++++++
 ginac/inifcns.h       |  6 ++++++
 ginac/normal.cpp      | 14 ++++++++++----
 ginsh/ginsh_parser.yy |  1 -
 5 files changed, 63 insertions(+), 7 deletions(-)

diff --git a/ginac/function.pl b/ginac/function.pl
index 4a218bbe..988206e9 100755
--- a/ginac/function.pl
+++ b/ginac/function.pl
@@ -508,7 +508,11 @@ protected:
     unsigned serial;
 };
 
-// utility macros
+// utility functions/macros
+inline const function &ex_to_function(const ex &e)
+{
+    return static_cast<const function &>(*e.bp);
+}
 
 #ifndef NO_NAMESPACE_GINAC
 
@@ -1041,7 +1045,7 @@ ex function::pderivative(unsigned diff_param) const // partial differentiation
     GINAC_ASSERT(serial<registered_functions().size());
     
     if (registered_functions()[serial].derivative_f==0) {
-        throw(std::logic_error(string("function::pderivative(") + registered_functions()[serial].name + "): no diff function defined"));
+        return Derivative(*this, diff_param);
     }
     switch (registered_functions()[serial].nparams) {
         // the following lines have been generated for max. ${maxargs} parameters
diff --git a/ginac/inifcns.cpp b/ginac/inifcns.cpp
index 55da24d0..e9e2cad1 100644
--- a/ginac/inifcns.cpp
+++ b/ginac/inifcns.cpp
@@ -166,9 +166,50 @@ static ex Order_series(const ex & x, const symbol & s, const ex & point, int ord
 	return pseries(s, point, new_seq);
 }
 
+// Differentiation is handled in function::derivative because of its special requirements
+
 REGISTER_FUNCTION(Order, eval_func(Order_eval).
                          series_func(Order_series));
 
+//////////
+// Inert differentiation
+//////////
+
+static ex Diff_eval(const ex & f, const ex & x)
+{
+	return Diff(f, x).hold();
+}
+
+static ex Diff_deriv(const ex & f, const ex & x, unsigned deriv_param)
+{
+	GINAC_ASSERT(deriv_param == 0 || deriv_param == 1);
+	if (deriv_param == 1)
+		return Diff(Diff(f, x), x);
+	else
+		return _ex0();
+}
+
+REGISTER_FUNCTION(Diff, eval_func(Diff_eval).
+                        derivative_func(Diff_deriv));
+
+//////////
+// Inert partial differentiation operator
+//////////
+
+static ex Derivative_eval(const ex & f, const ex & n)
+{
+	if (is_ex_exactly_of_type(n, numeric) && ex_to_numeric(n).is_nonneg_integer()) {
+		unsigned i = ex_to_numeric(n).to_int();
+		if (is_ex_exactly_of_type(f, function)) {
+			if (i < f.nops() && is_ex_exactly_of_type(f.op(i), symbol))
+				return Diff(f, f.op(i));
+		}
+	}
+	return Derivative(f, n).hold();
+}
+
+REGISTER_FUNCTION(Derivative, eval_func(Derivative_eval));
+
 //////////
 // Solve linear system
 //////////
diff --git a/ginac/inifcns.h b/ginac/inifcns.h
index 603edb3e..176f6794 100644
--- a/ginac/inifcns.h
+++ b/ginac/inifcns.h
@@ -123,6 +123,12 @@ DECLARE_FUNCTION_2P(binomial)
 /** Order term function (for truncated power series). */
 DECLARE_FUNCTION_1P(Order)
 
+/** Inert differentiation. */
+DECLARE_FUNCTION_2P(Diff)
+
+/** Inert partial differentiation operator. */
+DECLARE_FUNCTION_2P(Derivative)
+
 ex lsolve(const ex &eqns, const ex &symbols);
 
 ex ncpower(const ex &basis, unsigned exponent);
diff --git a/ginac/normal.cpp b/ginac/normal.cpp
index a5ebeb8b..d23b2289 100644
--- a/ginac/normal.cpp
+++ b/ginac/normal.cpp
@@ -1574,19 +1574,20 @@ ex power::normal(lst &sym_lst, lst &repl_lst, int level) const
 			// (a/b)^n -> {a^n, b^n}
 			return (new lst(power(n.op(0), exponent), power(n.op(1), exponent)))->setflag(status_flags::dynallocated);
 
-		} else if (exponent.info(info_flags::negint)) {
+		} else if (exponent.info(info_flags::negative)) {
 
 			// (a/b)^-n -> {b^n, a^n}
 			return (new lst(power(n.op(1), -exponent), power(n.op(0), -exponent)))->setflag(status_flags::dynallocated);
 		}
 
 	} else {
+
 		if (exponent.info(info_flags::positive)) {
 
-			// (a/b)^z -> {sym((a/b)^z), 1}
+			// (a/b)^x -> {sym((a/b)^x), 1}
 			return (new lst(replace_with_symbol(power(n.op(0) / n.op(1), exponent), sym_lst, repl_lst), _ex1()))->setflag(status_flags::dynallocated);
 
-		} else {
+		} else if (exponent.info(info_flags::negative)) {
 
 			if (n.op(1).is_equal(_ex1())) {
 
@@ -1595,9 +1596,14 @@ ex power::normal(lst &sym_lst, lst &repl_lst, int level) const
 
 			} else {
 
-				// (a/b)^-x -> {(b/a)^x, 1}
+				// (a/b)^-x -> {sym((b/a)^x), 1}
 				return (new lst(replace_with_symbol(power(n.op(1) / n.op(0), -exponent), sym_lst, repl_lst), _ex1()))->setflag(status_flags::dynallocated);
 			}
+
+		} else {	// exponent not numeric
+
+			// (a/b)^x -> {sym((a/b)^x, 1}
+			return (new lst(replace_with_symbol(power(n.op(0) / n.op(1), exponent), sym_lst, repl_lst), _ex1()))->setflag(status_flags::dynallocated);
 		}
     }
 }
diff --git a/ginsh/ginsh_parser.yy b/ginsh/ginsh_parser.yy
index fdb9bffa..6697d6f0 100644
--- a/ginsh/ginsh_parser.yy
+++ b/ginsh/ginsh_parser.yy
@@ -151,7 +151,6 @@ line	: ';'
 		cout << "You should have received a copy of the GNU General Public License along with\n";
 		cout << "this program. If not, write to the Free Software Foundation, 675 Mass Ave,\n";
 		cout << "Cambridge, MA 02139, USA.\n";
-
 	}
 	| T_XYZZY		{cout << "Nothing happens.\n";}
 	| T_INVENTORY		{cout << "You're not carrying anything.\n";}
-- 
2.44.0