From: Christian Bauer <Christian.Bauer@uni-mainz.de>
Date: Sun, 24 Aug 2003 22:55:54 +0000 (+0000)
Subject: - implemented object fusion as proposed by Richy
X-Git-Tag: release_1-2-0~125
X-Git-Url: https://www.ginac.de/ginac.git//ginac.git?p=ginac.git;a=commitdiff_plain;h=c69b9bb178e6445aae2cc19b2f188875a16e476b

- implemented object fusion as proposed by Richy
- unit(), content() and primpart() take a "const ex &" instead of a
  "const symbol &". degree(), coeff(), collect() etc. have dropped the
  restriction to symbols a long time ago, so there's no reason for these
  function to keep it.
---

diff --git a/ginac/ex.cpp b/ginac/ex.cpp
index e3e54c13..1af7f214 100644
--- a/ginac/ex.cpp
+++ b/ginac/ex.cpp
@@ -242,6 +242,19 @@ void ex::makewriteable()
 	GINAC_ASSERT(bp->refcount == 1);
 }
 
+/** Share equal objects between expressions.
+ *  @see ex::compare(const basic &) */
+void ex::share(const ex & other) const
+{
+	if ((bp->flags & status_flags::not_shareable) || (other.bp->flags & status_flags::not_shareable))
+		return;
+
+	if (bp->refcount <= other.bp->refcount)
+		bp = other.bp;
+	else
+		other.bp = bp;
+}
+
 /** Helper function for the ex-from-basic constructor. This is where GiNaC's
  *  automatic evaluator and memory management are implemented.
  *  @see ex::ex(const basic &) */
diff --git a/ginac/ex.h b/ginac/ex.h
index 38dcf732..ee891a2f 100644
--- a/ginac/ex.h
+++ b/ginac/ex.h
@@ -304,11 +304,11 @@ public:
 	ex numer_denom() const;
 
 	// polynomial algorithms
-	ex unit(const symbol &x) const;
-	ex content(const symbol &x) const;
+	ex unit(const ex &x) const;
+	ex content(const ex &x) const;
 	numeric integer_content() const;
-	ex primpart(const symbol &x) const;
-	ex primpart(const symbol &x, const ex &cont) const;
+	ex primpart(const ex &x) const;
+	ex primpart(const ex &x, const ex &cont) const;
 	ex smod(const numeric &xi) const { return bp->smod(xi); }
 	numeric max_coefficient() const;
 
@@ -345,6 +345,7 @@ private:
 	static basic & construct_from_double(double d);
 	static ptr<basic> construct_from_string_and_lst(const std::string &s, const ex &l);
 	void makewriteable();
+	void share(const ex & other) const;
 
 #ifdef OBSCURE_CINT_HACK
 public:
@@ -368,7 +369,7 @@ protected:
 // member variables
 
 private:
-	ptr<basic> bp;      ///< pointer to basic object managed by this
+	mutable ptr<basic> bp;  ///< pointer to basic object managed by this
 
 #ifdef OBSCURE_CINT_HACK
 public:
@@ -481,7 +482,14 @@ int ex::compare(const ex & other) const
 {
 	if (bp == other.bp)  // trivial case: both expressions point to same basic
 		return 0;
-	return bp->compare(*other.bp);
+	const int cmpval = bp->compare(*other.bp);
+	if (cmpval == 0) {
+		// Expressions point to different, but equal, trees: conserve
+		// memory and make subsequent compare() operations faster by
+		// making both expression point to the same tree.
+		share(other);
+	}
+	return cmpval;
 }
 
 inline