From 886ff58c2675aee6bd37469ce966924b40cc448d Mon Sep 17 00:00:00 2001
From: Jens Vollinga <vollinga@thep.physik.uni-mainz.de>
Date: Wed, 5 Sep 2007 16:52:25 +0000
Subject: [PATCH] Added example for mystring class [Sheplyakov].

---
 doc/examples/Makefile.am  |   3 +-
 doc/examples/mystring.cpp | 103 ++++++++++++++++++++++++++++++++++++++
 doc/tutorial/ginac.texi   |   3 +-
 3 files changed, 107 insertions(+), 2 deletions(-)
 create mode 100644 doc/examples/mystring.cpp

diff --git a/doc/examples/Makefile.am b/doc/examples/Makefile.am
index 5ee2c5d3..e63da35b 100644
--- a/doc/examples/Makefile.am
+++ b/doc/examples/Makefile.am
@@ -1,6 +1,7 @@
 ## Process this file with automake to produce Makefile.in
 
-EXFILES = archive1.cpp compile1.cpp compile2.cpp compile3.cpp lanczos.cpp
+EXFILES = archive1.cpp compile1.cpp compile2.cpp compile3.cpp lanczos.cpp \
+ mystring.cpp
 
 TEXI = ginac-examples.texi
 
diff --git a/doc/examples/mystring.cpp b/doc/examples/mystring.cpp
new file mode 100644
index 00000000..e9d12591
--- /dev/null
+++ b/doc/examples/mystring.cpp
@@ -0,0 +1,103 @@
+/**
+ * @file mystring.cpp Example of extending GiNaC: writing new classes
+ */
+#include <iostream>
+#include <string>   
+#include <stdexcept>
+using namespace std;
+
+#include <ginac/ginac.h>
+using namespace GiNaC;
+
+class mystring : public basic
+{
+	GINAC_DECLARE_REGISTERED_CLASS(mystring, basic)
+public:
+	mystring(const string &s);
+	mystring(const char *s);
+	ex eval(int level) const;
+
+private:
+	string str;
+
+protected:
+	void do_print(const print_context &c, unsigned level = 0) const;
+
+};
+
+GINAC_IMPLEMENT_REGISTERED_CLASS_OPT(mystring, basic,
+  print_func<print_context>(&mystring::do_print))
+
+// ctors
+mystring::mystring() : inherited(&mystring::tinfo_static) { }
+mystring::mystring(const string &s) : inherited(&mystring::tinfo_static), str(s) { }
+mystring::mystring(const char *s) : inherited(&mystring::tinfo_static), str(s) { }
+
+// comparison
+int mystring::compare_same_type(const basic &other) const
+{
+	const mystring &o = static_cast<const mystring &>(other);
+	int cmpval = str.compare(o.str);
+	if (cmpval == 0)
+		return 0;
+	else if (cmpval < 0)
+		return -1;
+	else
+		return 1;
+}
+
+// archiving/unarchiving
+mystring::mystring(const archive_node &n, lst &sym_lst) : inherited(n, sym_lst)
+{
+	n.find_string("string", str);
+}
+
+void mystring::archive(archive_node &n) const
+{
+	inherited::archive(n);
+	n.add_string("string", str);
+}
+
+ex mystring::unarchive(const archive_node &n, lst &sym_lst)
+{
+	return (new mystring(n, sym_lst))->setflag(status_flags::dynallocated);
+}
+
+// printing
+void mystring::do_print(const print_context &c, unsigned level) const
+{
+	// print_context::s is a reference to an ostream
+	c.s << '\"' << str << '\"';
+}
+
+/**
+ * evaluation: all strings automatically converted to lowercase with
+ * non-alphabetic characters stripped, and empty strings removed
+ */
+ex mystring::eval(int level) const
+{
+	string new_str;
+	for (size_t i=0; i<str.length(); i++) {
+		char c = str[i];
+		if (c >= 'A' && c <= 'Z') 
+			new_str += tolower(c);
+		else if (c >= 'a' && c <= 'z')
+			new_str += c;
+	}
+
+	if (new_str.length() == 0)
+		return 0;
+	else
+		return mystring(new_str).hold();
+}
+
+int main(int argc, char** argv)
+{
+	ex e = mystring("Hello, world!");
+	cout << is_a<mystring>(e) << endl;
+	cout << ex_to<basic>(e).class_name() << endl;
+	cout << e << endl;
+	ex another = pow(mystring("One string"), 2*sin(Pi-mystring("Another string")));
+	cout << another << endl;
+	return 0;
+}
diff --git a/doc/tutorial/ginac.texi b/doc/tutorial/ginac.texi
index a6befadb..b2038db5 100644
--- a/doc/tutorial/ginac.texi
+++ b/doc/tutorial/ginac.texi
@@ -7823,7 +7823,8 @@ Now we will start implementing a new class @code{mystring} that allows
 placing character strings in algebraic expressions (this is not very useful,
 but it's just an example). This class will be a direct subclass of
 @code{basic}. You can use this sample implementation as a starting point
-for your own classes.
+for your own classes @footnote{The self-contained source for this example is
+included in GiNaC, see the @file{doc/examples/mystring.cpp} file.}.
 
 The code snippets given here assume that you have included some header files
 as follows:
-- 
2.44.0