From cbec8852eaab9a2a578d082698d29432ed43134d Mon Sep 17 00:00:00 2001
From: Christian Bauer <Christian.Bauer@uni-mainz.de>
Date: Thu, 10 Jun 2004 02:17:13 +0000
Subject: [PATCH] map() doesn't allocate a new object unless necessary

---
 ginac/basic.cpp      | 25 ++++++++++++++++++-------
 ginac/idx.cpp        | 15 ++++++++++-----
 ginac/power.cpp      |  9 ++++++++-
 ginac/relational.cpp |  9 ++++++++-
 4 files changed, 44 insertions(+), 14 deletions(-)

diff --git a/ginac/basic.cpp b/ginac/basic.cpp
index 038cd7b5..b9689851 100644
--- a/ginac/basic.cpp
+++ b/ginac/basic.cpp
@@ -307,12 +307,23 @@ ex basic::map(map_function & f) const
 	if (num == 0)
 		return *this;
 
-	basic *copy = duplicate();
-	copy->setflag(status_flags::dynallocated);
-	copy->clearflag(status_flags::hash_calculated | status_flags::expanded);
-	for (size_t i=0; i<num; i++)
-		copy->let_op(i) = f(copy->op(i));
-	return *copy;
+	basic *copy = NULL;
+	for (size_t i=0; i<num; i++) {
+		const ex & o = op(i);
+		const ex & n = f(o);
+		if (!are_ex_trivially_equal(o, n)) {
+			if (copy == NULL)
+				copy = duplicate();
+			copy->let_op(i) = n;
+		}
+	}
+
+	if (copy) {
+		copy->setflag(status_flags::dynallocated);
+		copy->clearflag(status_flags::hash_calculated | status_flags::expanded);
+		return *copy;
+	} else
+		return *this;
 }
 
 /** Return degree of highest power in object s. */
@@ -781,7 +792,7 @@ unsigned basic::calchash() const
 struct expand_map_function : public map_function {
 	unsigned options;
 	expand_map_function(unsigned o) : options(o) {}
-	ex operator()(const ex & e) { return expand(e, options); }
+	ex operator()(const ex & e) { return e.expand(options); }
 };
 
 /** Expand expression, i.e. multiply it out and return the result as a new
diff --git a/ginac/idx.cpp b/ginac/idx.cpp
index 1aba28bf..c95c07c7 100644
--- a/ginac/idx.cpp
+++ b/ginac/idx.cpp
@@ -242,11 +242,16 @@ ex idx::op(size_t i) const
 
 ex idx::map(map_function & f) const
 {
-	idx *copy = duplicate();
-	copy->setflag(status_flags::dynallocated);
-	copy->clearflag(status_flags::hash_calculated);
-	copy->value = f(value);
-	return *copy;
+	const ex &mapped_value = f(value);
+	if (are_ex_trivially_equal(value, mapped_value))
+		return *this;
+	else {
+		idx *copy = duplicate();
+		copy->setflag(status_flags::dynallocated);
+		copy->clearflag(status_flags::hash_calculated);
+		copy->value = mapped_value;
+		return *copy;
+	}
 }
 
 /** Returns order relation between two indices of the same type. The order
diff --git a/ginac/power.cpp b/ginac/power.cpp
index aa0b082a..309d529a 100644
--- a/ginac/power.cpp
+++ b/ginac/power.cpp
@@ -246,7 +246,14 @@ ex power::op(size_t i) const
 
 ex power::map(map_function & f) const
 {
-	return (new power(f(basis), f(exponent)))->setflag(status_flags::dynallocated);
+	const ex &mapped_basis = f(basis);
+	const ex &mapped_exponent = f(exponent);
+
+	if (!are_ex_trivially_equal(basis, mapped_basis)
+	 || !are_ex_trivially_equal(exponent, mapped_exponent))
+		return (new power(mapped_basis, mapped_exponent))->setflag(status_flags::dynallocated);
+	else
+		return *this;
 }
 
 int power::degree(const ex & s) const
diff --git a/ginac/relational.cpp b/ginac/relational.cpp
index 87acde42..86e2c2e8 100644
--- a/ginac/relational.cpp
+++ b/ginac/relational.cpp
@@ -164,7 +164,14 @@ ex relational::op(size_t i) const
 
 ex relational::map(map_function & f) const
 {
-	return (new relational(f(lh), f(rh), o))->setflag(status_flags::dynallocated);
+	const ex &mapped_lh = f(lh);
+	const ex &mapped_rh = f(rh);
+
+	if (!are_ex_trivially_equal(lh, mapped_lh)
+	 || !are_ex_trivially_equal(rh, mapped_rh))
+		return (new relational(mapped_lh, mapped_rh, o))->setflag(status_flags::dynallocated);
+	else
+		return *this;
 }
 
 ex relational::eval(int level) const
-- 
2.49.0