From ece407276fc0f844b2cfcd51838e1cbe83a2d70c Mon Sep 17 00:00:00 2001
From: Chris Dams <Chris.Dams@mi.infn.it>
Date: Mon, 19 Jun 2006 15:29:43 +0000
Subject: [PATCH] Made class possymbol for positive symbols and documented it.

---
 doc/tutorial/ginac.texi | 10 ++++++++--
 ginac/symbol.cpp        | 21 +++++++++++++++++++++
 ginac/symbol.h          | 23 +++++++++++++++++++++++
 3 files changed, 52 insertions(+), 2 deletions(-)

diff --git a/doc/tutorial/ginac.texi b/doc/tutorial/ginac.texi
index 26f004ed..bdea81b8 100644
--- a/doc/tutorial/ginac.texi
+++ b/doc/tutorial/ginac.texi
@@ -1155,11 +1155,17 @@ in the complex domain.  As a consequence, operations like complex conjugation,
 for example (@pxref{Complex expressions}), do @emph{not} evaluate if applied
 to such symbols. Likewise @code{log(exp(x))} does not evaluate to @code{x},
 because of the unknown imaginary part of @code{x}.
-On the other hand, if you are sure that your symbols will hold only real values, you
-would like to have such functions evaluated. Therefore GiNaC allows you to specify
+On the other hand, if you are sure that your symbols will hold only real
+values, you would like to have such functions evaluated. Therefore GiNaC
+allows you to specify
 the domain of the symbol. Instead of @code{symbol x("x");} you can write
 @code{realsymbol x("x");} to tell GiNaC that @code{x} stands in for real values.
 
+@cindex @code{possymbol()}
+Furthermore, it is also possible to declare a symbol as positive. This will,
+for instance, enable the automatic simplification of @code{abs(x)} into 
+@code{x}. This is done by declaying the symbol as @code{possymbol x("x");}.
+
 
 @node Numbers, Constants, Symbols, Basic concepts
 @c    node-name, next, previous, up
diff --git a/ginac/symbol.cpp b/ginac/symbol.cpp
index 7e3b49d8..bf58fd4b 100644
--- a/ginac/symbol.cpp
+++ b/ginac/symbol.cpp
@@ -57,6 +57,13 @@ realsymbol::realsymbol()
 	domain = domain::real;
 }
 
+// possymbol
+
+possymbol::possymbol()
+{
+	domain = domain::positive;
+}
+
 //////////
 // other constructors
 //////////
@@ -103,6 +110,20 @@ realsymbol::realsymbol(const std::string & initname, unsigned rt, tinfo_t rtt, u
 realsymbol::realsymbol(const std::string & initname, const std::string & texname, unsigned rt, tinfo_t rtt, unsigned domain)
  : symbol(initname, texname, rt, rtt, domain) { }
 
+// possymbol
+	
+possymbol::possymbol(const std::string & initname, unsigned domain)
+ : symbol(initname, domain) { }
+
+possymbol::possymbol(const std::string & initname, const std::string & texname, unsigned domain)
+ : symbol(initname, texname, domain) { }
+
+possymbol::possymbol(const std::string & initname, unsigned rt, tinfo_t rtt, unsigned domain)
+ : symbol(initname, rt, rtt, domain) { }
+
+possymbol::possymbol(const std::string & initname, const std::string & texname, unsigned rt, tinfo_t rtt, unsigned domain)
+ : symbol(initname, texname, rt, rtt, domain) { }
+
 //////////
 // archiving
 //////////
diff --git a/ginac/symbol.h b/ginac/symbol.h
index 90013144..2a5ae5cc 100644
--- a/ginac/symbol.h
+++ b/ginac/symbol.h
@@ -41,6 +41,7 @@ class symbol : public basic
 	GINAC_DECLARE_REGISTERED_CLASS(symbol, basic)
 
 	friend class realsymbol;
+	friend class possymbol;
 
 // types
 	
@@ -127,6 +128,19 @@ public:
 };
 
 
+/** Specialization of symbol to real domain */
+class possymbol : public symbol
+{
+	// constructors
+public:
+	possymbol();
+	explicit possymbol(const std::string & initname, unsigned domain = domain::positive);
+	possymbol(const std::string & initname, const std::string & texname, unsigned domain = domain::positive);
+	possymbol(const std::string & initname, unsigned rt, tinfo_t rtt, unsigned domain = domain::positive);
+	possymbol(const std::string & initname, const std::string & texname, unsigned rt, tinfo_t rtt, unsigned domain = domain::positive);
+};
+
+
 // utility functions
 
 /** Specialization of is_exactly_a<realsymbol>(obj) for realsymbol objects. */
@@ -138,6 +152,15 @@ template<> inline bool is_exactly_a<realsymbol>(const basic & obj)
 	return domain==domain::real || domain==domain::positive;
 }
 
+/** Specialization of is_exactly_a<possymbol>(obj) for possymbol objects. */
+template<> inline bool is_exactly_a<possymbol>(const basic & obj)
+{
+	if (obj.tinfo() != &symbol::tinfo_static)
+		return false;
+	unsigned domain = static_cast<const symbol &>(obj).get_domain();
+	return domain == domain::positive;
+}
+
 // wrapper functions around member functions
 inline void unassign(symbol & symarg)
 { symarg.unassign(); }
-- 
2.44.0