From 05157f89a3db97fff79e33fd53156b380107011f Mon Sep 17 00:00:00 2001
From: Alexei Sheplyakov <varg@theor.jinr.ru>
Date: Sun, 14 Sep 2008 03:19:05 +0400
Subject: [PATCH] [bugfix]: parser::parse_unary_expr() parses '-a-b' correctly
 now.

Also added regression test.
---
 check/Makefile.am       |  4 +++
 check/parser_bugs.cpp   | 59 +++++++++++++++++++++++++++++++++++++++++
 ginac/parser/parser.cpp | 31 ++++++++++++----------
 ginac/parser/parser.hpp |  2 +-
 4 files changed, 81 insertions(+), 15 deletions(-)
 create mode 100644 check/parser_bugs.cpp

diff --git a/check/Makefile.am b/check/Makefile.am
index de86f5cd..87b489d1 100644
--- a/check/Makefile.am
+++ b/check/Makefile.am
@@ -8,6 +8,7 @@ CHECKS = check_numeric \
 EXAMS = exam_paranoia \
 	exam_heur_gcd \
 	match_bug \
+	parser_bugs \
 	exam_numeric_archive \
 	exam_numeric \
 	exam_powerlaws  \
@@ -78,6 +79,9 @@ exam_heur_gcd_LDADD = ../ginac/libginac.la
 match_bug_SOURCES = match_bug.cpp error_report.hpp
 match_bug_LDADD = ../ginac/libginac.la
 
+parser_bugs_SOURCES = parser_bugs.cpp
+parser_bugs_LDADD = ../ginac/libginac.la
+
 exam_numeric_archive_SOURCES = numeric_archive.cpp
 exam_numeric_archive_LDADD = ../ginac/libginac.la
 
diff --git a/check/parser_bugs.cpp b/check/parser_bugs.cpp
new file mode 100644
index 00000000..340fe20f
--- /dev/null
+++ b/check/parser_bugs.cpp
@@ -0,0 +1,59 @@
+/// @file parser_a_b.cpp Check for some silly bugs in the parser.
+#include "ginac.h"
+#include <string>
+#include <iostream>
+#include <stdexcept>
+#include <sstream>
+using namespace GiNaC;
+
+// - a - b was misparsed as -a + b due to a bug in parser::parse_unary_expr()
+static int check1(std::ostream& err_str)
+{
+	const std::string srep("-a-b");
+	parser reader;
+	ex e = reader(srep);
+	ex a = reader.get_syms()["a"];
+	ex b = reader.get_syms()["b"];
+	ex g = - a - b;
+	ex d = (e - g).expand();
+	if (!d.is_zero()) {
+		err_str << "\"" << srep << "\" was misparsed as \""
+			<< e << "\"" << std::endl;
+		return 1;
+	}
+	return 0;
+}
+
+/// Parser was rejecting the valid expression '5 - (3*x)/10'.
+static int check2(std::ostream& err_str)
+{
+	const std::string srep("5-(3*x)/10");
+	parser reader;
+	ex e = reader(srep);
+	ex x = reader.get_syms()["x"];
+	ex g = 5 - (3*x)/10;
+	ex d = (e - g).expand();
+	if (!d.is_zero()) {
+		err_str << "\"" << srep << "\" was misparsed as \""
+			<< e << "\"" << std::endl;
+		return 1;
+	}
+	return 0;
+}
+
+int main(int argc, char** argv)
+{
+	std::cout << "checking for parser bugs. " << std::flush;
+	std::ostringstream err_str;
+	int errors = 0;
+	errors += check1(err_str);
+	errors += check2(err_str);
+	if (errors) {
+		std::cout << "Yes, unfortunately:" << std::endl;
+		std::cout << err_str.str();
+	} else {
+		std::cout << "Not found. ";
+	}
+	return errors;
+}
+
diff --git a/ginac/parser/parser.cpp b/ginac/parser/parser.cpp
index 0ee682ab..f48d37fd 100644
--- a/ginac/parser/parser.cpp
+++ b/ginac/parser/parser.cpp
@@ -60,21 +60,25 @@ ex parser::parse_paren_expr()
 }
 
 extern numeric* _num_1_p;
+extern ex _ex0;
 
 /// unary_expr: [+-] expression
-ex parser::parse_unary_expr(const int s)
+ex parser::parse_unary_expr()
 {
-	// consume '-' (or '+')
-	get_next_tok();
-	ex v = parse_expression();
-	switch (s) {
-		case '-':
-			return (new mul(v, *_num_1_p))->setflag(status_flags::dynallocated);
-		case '+':
-			return v;
-		default:
-			Parse_error_("invalid unary operator \"" << char(s) << "\"");
-	}
+	// Unlike most other parse_* method this one does NOT consume
+	// current token so parse_binop_rhs() knows what kind of operator
+	// is being parsed.
+	
+	// There are different kinds of expressions which need to be handled:
+	// -a+b 
+	// -(a) 
+	// +a
+	// +(a)
+	// Delegete the work to parse_binop_rhs(), otherwise we end up
+	// duplicating it here. 
+	ex lhs = _ex0; // silly trick
+	ex e = parse_binop_rhs(0, lhs);
+	return e;
 }
 
 /// primary: identifier_expr | number_expr | paren_expr | unary_expr 
@@ -88,9 +92,8 @@ ex parser::parse_primary()
 		case '(': 
 			 return parse_paren_expr();
 		case '-':
-			 return parse_unary_expr('-');
 		case '+':
-			 return parse_unary_expr('+');
+			 return parse_unary_expr();
 		case lexer::token_type::literal:
 			 return parse_literal_expr();
 		case lexer::token_type::eof:
diff --git a/ginac/parser/parser.hpp b/ginac/parser/parser.hpp
index eb50adc0..b46ec650 100644
--- a/ginac/parser/parser.hpp
+++ b/ginac/parser/parser.hpp
@@ -49,7 +49,7 @@ class parser
 	ex parse_number_expr();
 
 	/// unary_expr: [+-] expression
-	ex parse_unary_expr(const int c);
+	ex parse_unary_expr();
 
 	/// literal_expr: 'I' | 'Pi' | 'Euler' | 'Catalan'
 	ex parse_literal_expr();
-- 
2.44.0