- The default implementations of evalf(), diff(), normal() and expand() use

[ginac.git] / ginac / add.cpp

diff --git a/ginac/add.cpp b/ginac/add.cpp
index 647de1722c7065c2d735f7093b187880d42c4203..31e2f8fc5b3e540dd80667bed303cbfd8c8f3444 100644 (file)
--- a/ginac/add.cpp
+++ b/ginac/add.cpp
@@ -381,10 +381,19 @@ ex add::simplify_ncmul(const exvector & v) const
 
 /** Implementation of ex::diff() for a sum. It differentiates each term.
  *  @see ex::diff */
-ex add::derivative(const symbol & s) const
+ex add::derivative(const symbol & y) const
 {
-       // D(a+b+c)=D(a)+D(b)+D(c)
-       return (new add(diffchildren(s)))->setflag(status_flags::dynallocated);
+       epvector *s = new epvector();
+       s->reserve(seq.size());
+       
+       // Only differentiate the "rest" parts of the expairs. This is faster
+       // than the default implementation in basic::derivative() although
+       // if performs the same function (differentiate each term).
+       for (epvector::const_iterator it=seq.begin(); it!=seq.end(); ++it) {
+               s->push_back(combine_ex_with_coeff_to_pair((*it).rest.diff(y),
+                                                          (*it).coeff));
+       }
+       return (new add(s, _ex0()))->setflag(status_flags::dynallocated);
 }
 
 int add::compare_same_type(const basic & other) const
@@ -492,10 +501,9 @@ ex add::expand(unsigned options) const
                return *this;
        
        epvector * vp = expandchildren(options);
-       if (vp==0) {
+       if (vp == NULL) {
                // the terms have not changed, so it is safe to declare this expanded
-               setflag(status_flags::expanded);
-               return *this;
+               return this->setflag(status_flags::expanded);
        }
        
        return (new add(vp,overall_coeff))->setflag(status_flags::expanded | status_flags::dynallocated);