Spirit: Added a new Qi example

[SVN r59375]

example/qi/Jamfile

@@ -32,6 +32,7 @@ exe key_value_sequence_empty_value : key_value_sequence_empty_value.cpp ;
 
 exe iter_pos_parser : iter_pos_parser.cpp ;
 exe boost_array : boost_array.cpp ;
+exe display_attribute_type : display_attribute_type.cpp ;
 
 exe calculator1 : calc1.cpp ;
 exe calculator2 : calc2.cpp ;

example/qi/display_attribute_type.cpp

@@ -0,0 +1,22 @@
+//  Copyright (c) 2001-2010 Hartmut Kaiser
+// 
+//  Distributed under the Boost Software License, Version 1.0. (See accompanying 
+//  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+//  This example implements a simple utility allowing to print the attribute 
+//  type as it is exposed by an arbitrary Qi parser expression. Just insert 
+//  your expression below, compile and run this example to see what Qi is 
+//  seeing!
+
+#include "display_attribute_type.hpp"
+
+namespace qi = boost::spirit::qi;
+
+int main()
+{
+    tools::display_attribute_of_parser(
+        std::cerr,                // put the required output stream here
+        qi::int_ >> qi::double_   // put your parser expression here
+    );
+    return 0;
+}

example/qi/display_attribute_type.hpp

@@ -0,0 +1,49 @@
+//  Copyright (c) 2001-2010 Hartmut Kaiser
+// 
+//  Distributed under the Boost Software License, Version 1.0. (See accompanying 
+//  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+//  This example implements a simple utility allowing to print the attribute 
+//  type as it is exposed by an arbitrary Qi parser expression. Just insert 
+//  your expression below, compile and run this example to see what Qi is 
+//  seeing!
+
+#if !defined (DISPLAY_ATTRIBUTE_OF_PARSER_JAN_2010_30_0722PM)
+#define DISPLAY_ATTRIBUTE_OF_PARSER_JAN_2010_30_0722PM
+
+#include <iostream>
+#include <boost/spirit/include/qi.hpp>
+
+namespace tools
+{
+    namespace spirit = boost::spirit;
+
+    template <typename Expr, typename Iterator = spirit::unused_type>
+    struct attribute_of_parser
+    {
+        typedef typename spirit::result_of::compile<
+            spirit::qi::domain, Expr
+        >::type parser_expression_type;
+
+        typedef typename spirit::traits::attribute_of<
+            parser_expression_type, spirit::unused_type, Iterator
+        >::type type;
+    };
+
+    template <typename T>
+    void display_attribute_of_parser(T const &) 
+    {
+        typedef typename attribute_of_parser<T>::type type;
+        std::cout << typeid(type).name() << std::endl;
+    }
+
+    template <typename T>
+    void display_attribute_of_parser(std::ostream& os, T const &) 
+    {
+        typedef typename attribute_of_parser<T>::type type;
+        std::cout << typeid(type).name() << std::endl;
+    }
+}
+
+#endif
+