- fixed bug in normal(): normal(x^a) became (x^(-a))^(-1)
[ginac.git] / ginac / inifcns.cpp
index 55da24d052de66e3559a5469a87f57b8b0883d56..e9e2cad1421b0bbcbccd985d487f61994d58d62a 100644 (file)
@@ -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
 //////////