From 454b1d9b6baeab44188a5bee5725a9816afe7a5f Mon Sep 17 00:00:00 2001
From: Christian Bauer <Christian.Bauer@uni-mainz.de>
Date: Thu, 20 Feb 2003 17:50:43 +0000
Subject: [PATCH] let_op() is no longer the default implementation of op().
 Rationale: let_op() needs to clear status_flags::hash_calculated, otherwise
 we could end up with equal objects that have different hash values. But
 clearing hash_calculated on a read-only op() access would be inefficient.
 let_op() is now only implemented by lst and matrix.

---
 ginac/basic.cpp         |  3 ++-
 ginac/container.pl      | 23 +++++++++++++++++++++--
 ginac/expairseq.cpp     |  5 -----
 ginac/expairseq.h       |  1 -
 ginac/exprseq_suppl.cpp |  4 ++--
 ginac/idx.cpp           | 11 ++++++++++-
 ginac/idx.h             |  3 ++-
 ginac/matrix.cpp        | 10 ++++++++++
 ginac/matrix.h          |  1 +
 ginac/pseries.cpp       |  6 +-----
 ginac/pseries.h         |  1 -
 11 files changed, 49 insertions(+), 19 deletions(-)

diff --git a/ginac/basic.cpp b/ginac/basic.cpp
index 9fd73982..70237930 100644
--- a/ginac/basic.cpp
+++ b/ginac/basic.cpp
@@ -179,12 +179,13 @@ unsigned basic::nops() const
 /** Return operand/member at position i. */
 ex basic::op(int i) const
 {
-	return (const_cast<basic *>(this))->let_op(i);
+	throw(std::runtime_error(std::string("op() not implemented by ") + class_name()));
 }
 
 /** Return modifyable operand/member at position i. */
 ex & basic::let_op(int i)
 {
+	ensure_if_modifiable();
 	throw(std::runtime_error(std::string("let_op() not implemented by ") + class_name()));
 }
 
diff --git a/ginac/container.pl b/ginac/container.pl
index c30342d9..84c0a49d 100755
--- a/ginac/container.pl
+++ b/ginac/container.pl
@@ -106,12 +106,29 @@ END_OF_SORT_IMPLEMENTATION
 }
 
 if ($let_op) {
-	$LET_OP_IMPLEMENTATION=<<END_OF_LET_OP_IMPLEMENTATION
+	$LET_OP_DEFINITION=<<END_OF_LET_OP_DEFINITION;
+	ex & let_op(int i);
+END_OF_LET_OP_DEFINITION
+
+	$LET_OP_IMPLEMENTATION=<<END_OF_LET_OP_IMPLEMENTATION;
+ex ${CONTAINER}::op(int i) const
+{
+	GINAC_ASSERT(i>=0);
+	GINAC_ASSERT(i<nops());
+
+	${STLT}::const_iterator it=seq.begin();
+	for (int j=0; j<i; j++) {
+		++it;
+	}
+	return *it;
+}
+
 ex & ${CONTAINER}::let_op(int i)
 {
 	GINAC_ASSERT(i>=0);
 	GINAC_ASSERT(i<nops());
 
+	ensure_if_modifiable();
 	${STLT}::iterator it=seq.begin();
 	for (int j=0; j<i; j++) {
 		++it;
@@ -120,6 +137,7 @@ ex & ${CONTAINER}::let_op(int i)
 }
 END_OF_LET_OP_IMPLEMENTATION
 } else {
+	$LET_OP_DEFINITION="";
 	$LET_OP_IMPLEMENTATION="// ${CONTAINER}::let_op() will be implemented by user elsewhere";
 }
 
@@ -238,7 +256,8 @@ public:
 	unsigned precedence(void) const {return 10;}
 	bool info(unsigned inf) const;
 	unsigned nops() const;
-	ex & let_op(int i);
+	ex op(int i) const;
+${LET_OP_DEFINITION}
 	ex map(map_function & f) const;
 	ex eval(int level=0) const;
 	ex subs(const lst & ls, const lst & lr, unsigned options = 0) const;
diff --git a/ginac/expairseq.cpp b/ginac/expairseq.cpp
index 228da90c..5c3c2fe7 100644
--- a/ginac/expairseq.cpp
+++ b/ginac/expairseq.cpp
@@ -292,11 +292,6 @@ ex expairseq::op(int i) const
 	return overall_coeff;
 }
 
-ex & expairseq::let_op(int i)
-{
-	throw(std::logic_error("let_op not defined for expairseq and derived classes (add, mul, ...)"));
-}
-
 ex expairseq::map(map_function &f) const
 {
 	epvector *v = new epvector;
diff --git a/ginac/expairseq.h b/ginac/expairseq.h
index 559ca1e8..add8a8f9 100644
--- a/ginac/expairseq.h
+++ b/ginac/expairseq.h
@@ -91,7 +91,6 @@ public:
 	bool info(unsigned inf) const;
 	unsigned nops() const;
 	ex op(int i) const;
-	ex & let_op(int i);
 	ex map(map_function & f) const;
 	ex eval(int level=0) const;
 	ex to_rational(lst &repl_lst) const;
diff --git a/ginac/exprseq_suppl.cpp b/ginac/exprseq_suppl.cpp
index 29bb549a..e348853c 100644
--- a/ginac/exprseq_suppl.cpp
+++ b/ginac/exprseq_suppl.cpp
@@ -33,11 +33,11 @@ bool exprseq::info(unsigned inf) const
 	return basic::info(inf);
 }
 
-ex & exprseq::let_op(int i)
+ex exprseq::op(int i) const
 {
 	GINAC_ASSERT(i>=0);
 	GINAC_ASSERT(i<nops());
-	
+
 	return seq[i];
 }
 
diff --git a/ginac/idx.cpp b/ginac/idx.cpp
index 2cd3eae6..2323c29c 100644
--- a/ginac/idx.cpp
+++ b/ginac/idx.cpp
@@ -275,12 +275,21 @@ unsigned idx::nops() const
 	return 1;
 }
 
-ex & idx::let_op(int i)
+ex idx::op(int i) const
 {
 	GINAC_ASSERT(i == 0);
 	return value;
 }
 
+ex idx::map(map_function & f) const
+{
+	idx *copy = static_cast<idx *>(duplicate());
+	copy->setflag(status_flags::dynallocated);
+	copy->clearflag(status_flags::hash_calculated);
+	copy->value = f(value);
+	return *copy;
+}
+
 /** Returns order relation between two indices of the same type. The order
  *  must be such that dummy indices lie next to each other. */
 int idx::compare_same_type(const basic & other) const
diff --git a/ginac/idx.h b/ginac/idx.h
index fe7b5194..7fc743b5 100644
--- a/ginac/idx.h
+++ b/ginac/idx.h
@@ -51,7 +51,8 @@ public:
 	void print(const print_context & c, unsigned level = 0) const;
 	bool info(unsigned inf) const;
 	unsigned nops() const;
-	ex & let_op(int i);
+	ex op(int i) const;
+	ex map(map_function & f) const;
 	ex evalf(int level = 0) const;
 	ex subs(const lst & ls, const lst & lr, unsigned options = 0) const;
 
diff --git a/ginac/matrix.cpp b/ginac/matrix.cpp
index 57cd8894..67d99c97 100644
--- a/ginac/matrix.cpp
+++ b/ginac/matrix.cpp
@@ -199,11 +199,21 @@ unsigned matrix::nops() const
 }
 
 /** returns matrix entry at position (i/col, i%col). */
+ex matrix::op(int i) const
+{
+	GINAC_ASSERT(i>=0);
+	GINAC_ASSERT(i<nops());
+	
+	return m[i];
+}
+
+/** returns writable matrix entry at position (i/col, i%col). */
 ex & matrix::let_op(int i)
 {
 	GINAC_ASSERT(i>=0);
 	GINAC_ASSERT(i<nops());
 	
+	ensure_if_modifiable();
 	return m[i];
 }
 
diff --git a/ginac/matrix.h b/ginac/matrix.h
index 5eb816bb..7fabe709 100644
--- a/ginac/matrix.h
+++ b/ginac/matrix.h
@@ -45,6 +45,7 @@ public:
 public:
 	void print(const print_context & c, unsigned level = 0) const;
 	unsigned nops() const;
+	ex op(int i) const;
 	ex & let_op(int i);
 	ex eval(int level=0) const;
 	ex evalm(void) const {return *this;}
diff --git a/ginac/pseries.cpp b/ginac/pseries.cpp
index 6077fd72..33b9cfdc 100644
--- a/ginac/pseries.cpp
+++ b/ginac/pseries.cpp
@@ -264,12 +264,8 @@ ex pseries::op(int i) const
 {
 	if (i < 0 || unsigned(i) >= seq.size())
 		throw (std::out_of_range("op() out of range"));
-	return seq[i].rest * power(var - point, seq[i].coeff);
-}
 
-ex & pseries::let_op(int i)
-{
-	throw (std::logic_error("let_op() not defined for pseries"));
+	return seq[i].rest * power(var - point, seq[i].coeff);
 }
 
 /** Return degree of highest power of the series.  This is usually the exponent
diff --git a/ginac/pseries.h b/ginac/pseries.h
index 37ac5796..17ae934a 100644
--- a/ginac/pseries.h
+++ b/ginac/pseries.h
@@ -46,7 +46,6 @@ public:
 	unsigned precedence(void) const {return 38;} // for clarity just below add::precedence
 	unsigned nops(void) const;
 	ex op(int i) const;
-	ex & let_op(int i);
 	int degree(const ex &s) const;
 	int ldegree(const ex &s) const;
 	ex coeff(const ex &s, int n = 1) const;
-- 
2.50.0