some changes to allow GiNaC to cooperate with cint:

[ginac.git] / ginac / diff.cpp

diff --git a/ginac/diff.cpp b/ginac/diff.cpp
index 7b4d489b76b6dc1a51e572c9326657282411f5d7..65ee609a27cc8d04a7c76c43a585dc473e397f00 100644 (file)
--- a/ginac/diff.cpp
+++ b/ginac/diff.cpp
@@ -37,7 +37,9 @@
 #include "series.h"
 #include "symbol.h"
 
+#ifndef NO_GINAC_NAMESPACE
 namespace GiNaC {
+#endif // ndef NO_GINAC_NAMESPACE
 
 /** Default implementation of ex::diff(). It prints and error message and returns a fail object.
  *  @see ex::diff */
@@ -175,17 +177,22 @@ ex power::diff(symbol const & s) const
 ex function::diff(symbol const & s) const
 {
     exvector new_seq;
-
-    if (serial == function_index_Order) {
-
+    
+    if (serial==function_index_Order) {
         // Order Term function only differentiates the argument
         return Order(seq[0].diff(s));
-
     } else {
-
         // Chain rule
+        ex arg_diff;
         for (unsigned i=0; i!=seq.size(); i++) {
-            new_seq.push_back(mul(pdiff(i), seq[i].diff(s)));
+            arg_diff = seq[i].diff(s);
+            // We apply the chain rule only when it makes sense.  This is not
+            // just for performance reasons but also to allow functions to
+            // throw when differentiated with respect to one of its arguments
+            // without running into trouble with our automatic full
+            // differentiation:
+            if (!arg_diff.is_zero())
+                new_seq.push_back(mul(pdiff(i), arg_diff));
         }
     }
     return add(new_seq);
@@ -228,16 +235,18 @@ ex ex::diff(symbol const & s, unsigned nth) const
 {
     GINAC_ASSERT(bp!=0);
 
-    if ( nth==0 ) {
+    if (nth==0) {
         return *this;
     }
 
     ex ndiff = bp->diff(s);
-    while ( nth>1 ) {
+    while (nth>1) {
         ndiff = ndiff.diff(s);
         --nth;
     }
     return ndiff;
 }
 
+#ifndef NO_GINAC_NAMESPACE
 } // namespace GiNaC
+#endif // ndef NO_GINAC_NAMESPACE