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

[ginac.git] / ginac / basic.cpp

diff --git a/ginac/basic.cpp b/ginac/basic.cpp
index e2a9320e9b098629017fff48aebfc35892292170..43dbf3366cebc54fb98a7b1810a889b9e5c89f97 100644 (file)
--- a/ginac/basic.cpp
+++ b/ginac/basic.cpp
@@ -293,6 +293,27 @@ ex basic::subs(const lst & ls, const lst & lr) const
     return *this;
 }
 
+/** Default interface of nth derivative ex::diff(s, n).  It should be called
+ *  instead of ::derivative(s) for first derivatives and for nth derivatives it
+ *  just recurses down.
+ *
+ *  @param s symbol to differentiate in
+ *  @param nth order of differentiation
+ *  @see ex::diff */
+ex basic::diff(const symbol & s, unsigned nth) const
+{
+    // FIXME: Check if it is evaluated!
+    if (!nth)
+        return ex(*this);
+    ex ndiff = derivative(s);
+    while (!ndiff.is_zero() &&    // stop differentiating zeroes
+           nth>1) {
+        ndiff = ndiff.diff(s);
+        --nth;
+    }
+    return ndiff;
+}
+
 exvector basic::get_indices(void) const
 {
     return exvector(); // return an empty exvector
@@ -305,6 +326,15 @@ ex basic::simplify_ncmul(const exvector & v) const
 
 // protected
 
+/** Default implementation of ex::diff(). It simply throws an error message.
+ *
+ *  @exception logic_error (differentiation not supported by this type)
+ *  @see ex::diff */
+ex basic::derivative(const symbol & s) const
+{
+    throw(std::logic_error("differentiation not supported by this type"));
+}
+
 int basic::compare_same_type(const basic & other) const
 {
     return compare_pointers(this, &other);
@@ -349,6 +379,7 @@ ex basic::expand(unsigned options) const
     return this->setflag(status_flags::expanded);
 }
 
+
 //////////
 // non-virtual functions in this class
 //////////