- diff() is now only defined on classes ex and basic, where it handles

[ginac.git] / ginac / ncmul.cpp

diff --git a/ginac/ncmul.cpp b/ginac/ncmul.cpp
index a970a8b2b3c5cd58cbb29fb5e6a79fa91afb41f6..7cd8014931db652672366b61bf9762ebb760603c 100644 (file)
--- a/ginac/ncmul.cpp
+++ b/ginac/ncmul.cpp
@@ -538,6 +538,13 @@ ex ncmul::thisexprseq(exvector * vp) const
 
 // protected
 
+/** Implementation of ex::diff() for a non-commutative product. It always returns 0.
+ *  @see ex::diff */
+ex ncmul::derivative(const symbol & s) const
+{
+    return _ex0();
+}
+
 int ncmul::compare_same_type(const basic & other) const
 {
     return inherited::compare_same_type(other);