synced to 1.2 (memory conservation)

[ginac.git] / ginac / ncmul.cpp

diff --git a/ginac/ncmul.cpp b/ginac/ncmul.cpp
index 005cc16f77369b29d67c9a93550a473d2ce4b566..3bc8b2145766e2755e6cc8060e10a9c892d2f4d2 100644 (file)
--- a/ginac/ncmul.cpp
+++ b/ginac/ncmul.cpp
@@ -127,7 +127,8 @@ typedef std::vector<int> intvector;
 ex ncmul::expand(unsigned options) const
 {
        // First, expand the children
-       exvector expanded_seq = expandchildren(options);
+       std::auto_ptr<exvector> vp = expandchildren(options);
+       const exvector &expanded_seq = vp.get() ? *vp : this->seq;
        
        // Now, look for all the factors that are sums and remember their
        // position and number of terms.
@@ -151,9 +152,13 @@ ex ncmul::expand(unsigned options) const
        }
 
        // If there are no sums, we are done
-       if (number_of_adds == 0)
-               return (new ncmul(expanded_seq, true))->
-                       setflag(status_flags::dynallocated | (options == 0 ? status_flags::expanded : 0));
+       if (number_of_adds == 0) {
+               if (vp.get())
+                       return (new ncmul(vp))->
+                               setflag(status_flags::dynallocated | (options == 0 ? status_flags::expanded : 0));
+               else
+                       return *this;
+       }
 
        // Now, form all possible products of the terms of the sums with the
        // remaining factors, and add them together
@@ -561,16 +566,34 @@ unsigned ncmul::return_type_tinfo() const
 // non-virtual functions in this class
 //////////
 
-exvector ncmul::expandchildren(unsigned options) const
+std::auto_ptr<exvector> ncmul::expandchildren(unsigned options) const
 {
-       exvector s;
-       s.reserve(seq.size());
-       exvector::const_iterator it = seq.begin(), itend = seq.end();
-       while (it != itend) {
-               s.push_back(it->expand(options));
-               it++;
+       const_iterator cit = this->seq.begin(), end = this->seq.end();
+       while (cit != end) {
+               const ex & expanded_ex = cit->expand(options);
+               if (!are_ex_trivially_equal(*cit, expanded_ex)) {
+
+                       // copy first part of seq which hasn't changed
+                       std::auto_ptr<exvector> s(new exvector(this->seq.begin(), cit));
+                       reserve(*s, this->seq.size());
+
+                       // insert changed element
+                       s->push_back(expanded_ex);
+                       ++cit;
+
+                       // copy rest
+                       while (cit != end) {
+                               s->push_back(cit->expand(options));
+                               ++cit;
+                       }
+
+                       return s;
+               }
+
+               ++cit;
        }
-       return s;
+
+       return std::auto_ptr<exvector>(0); // nothing has changed
 }
 
 const exvector & ncmul::get_factors() const