From f10b253437b350a2c5897bd7e65a27914a32f068 Mon Sep 17 00:00:00 2001
From: Christian Bauer <Christian.Bauer@uni-mainz.de>
Date: Thu, 10 Jun 2004 02:18:34 +0000
Subject: [PATCH] ncmul::expand() doesn't allocate a new object unless
 necessary

---
 ginac/ncmul.cpp | 47 +++++++++++++++++++++++++++++++++++------------
 ginac/ncmul.h   |  2 +-
 2 files changed, 36 insertions(+), 13 deletions(-)

diff --git a/ginac/ncmul.cpp b/ginac/ncmul.cpp
index 005cc16f..3bc8b214 100644
--- 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
diff --git a/ginac/ncmul.h b/ginac/ncmul.h
index 46a7aae1..436ae8c0 100644
--- a/ginac/ncmul.h
+++ b/ginac/ncmul.h
@@ -80,7 +80,7 @@ protected:
 	void do_print_csrc(const print_context & c, unsigned level) const;
 	size_t count_factors(const ex & e) const;
 	void append_factors(exvector & v, const ex & e) const;
-	exvector expandchildren(unsigned options) const;
+	std::auto_ptr<exvector> expandchildren(unsigned options) const;
 public:
 	const exvector & get_factors() const;
 };
-- 
2.49.0