[Boost-commit] svn:boost r56595 - trunk/libs/spirit/example/qi

Subject: [Boost-commit] svn:boost r56595 - trunk/libs/spirit/example/qi
From: hartmut.kaiser_at_[hidden]
Date: 2009-10-05 10:32:55

Author: hkaiser
Date: 2009-10-05 10:32:54 EDT (Mon, 05 Oct 2009)
New Revision: 56595
URL: http://svn.boost.org/trac/boost/changeset/56595

Log:
Spirit: added example demonstrating transform_attribute
Added:
   trunk/libs/spirit/example/qi/parse_date.cpp   (contents, props changed)
Text files modified: 
   trunk/libs/spirit/example/qi/CMakeLists.txt |     1 +                                       
   trunk/libs/spirit/example/qi/Jamfile        |     1 +                                       
   2 files changed, 2 insertions(+), 0 deletions(-)

Modified: trunk/libs/spirit/example/qi/CMakeLists.txt
==============================================================================
--- trunk/libs/spirit/example/qi/CMakeLists.txt	(original)
+++ trunk/libs/spirit/example/qi/CMakeLists.txt	2009-10-05 10:32:54 EDT (Mon, 05 Oct 2009)
@@ -23,6 +23,7 @@
 boost_add_executable( num_list3  num_list3.cpp )
 boost_add_executable( num_list4  num_list4.cpp )
 boost_add_executable( reorder_struct  reorder_struct.cpp )
+boost_add_executable( parse_date  parse_date.cpp )
 
 boost_add_executable( calc1  calc1.cpp )
 boost_add_executable( calc2  calc2.cpp )

Modified: trunk/libs/spirit/example/qi/Jamfile
==============================================================================
--- trunk/libs/spirit/example/qi/Jamfile	(original)
+++ trunk/libs/spirit/example/qi/Jamfile	2009-10-05 10:32:54 EDT (Mon, 05 Oct 2009)
@@ -24,6 +24,7 @@
 exe num_list3 : num_list3.cpp ;
 exe num_list4 : num_list4.cpp ;
 exe reorder_struct : reorder_struct.cpp ;
+exe parse_date : parse_date.cpp ;
 
 exe calculator1 : calc1.cpp ;
 exe calculator2 : calc2.cpp ;

Added: trunk/libs/spirit/example/qi/parse_date.cpp
==============================================================================
--- (empty file)
+++ trunk/libs/spirit/example/qi/parse_date.cpp	2009-10-05 10:32:54 EDT (Mon, 05 Oct 2009)
@@ -0,0 +1,123 @@
+/*=============================================================================
+    Copyright (c) 2001-2009 Hartmut Kaiser
+    Copyright (c) 2001-2009 Joel de Guzman
+
+    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 is not meant to be a sophisticated date parser. It's sole 
+// purpose is to demonstrate the intrinsic attribute transformation 
+// capabilities of a rule. 
+// 
+// Note how the rule exposes a fusion sequence, but gets passed an instance of
+// a boost::gregorian::date as the attribute. In order to make these types 
+// compatible for the rule we define a specialization of the customization 
+// point called 'transform_attribute'.
+
+#include <boost/config/warning_disable.hpp>
+#include <boost/spirit/include/qi.hpp>
+#include <boost/fusion/include/vector.hpp>
+#include <boost/date_time.hpp>
+
+// define custom transformation
+namespace boost { namespace spirit { namespace traits
+{
+    // This specialization of the customization point transform_attribute 
+    // allows to pass a boost::gregorian::date to a rule which is expecting
+    // a fusion sequence consisting out of three integers as its attribute.
+    template<>
+    struct transform_attribute<
+        boost::gregorian::date, fusion::vector<int, int, int> >
+    {
+        typedef fusion::vector<int, int, int> date_parts;
+
+        // The embedded typedef 'type' exposes the attribute as it will be 
+        // passed to the right hand side. 
+        typedef date_parts type;
+
+        // The function pre() is called for down-stream conversion of the
+        // attribute supplied to the rule to the attribute expected by the
+        // right hand side.
+        // The supplied attribute might have been pre-initialized by parsers
+        // (i.e. semantic actions) higher up the parser hierarchy (in the 
+        // grammar, in which case we would need to properly initialize the 
+        // returned value from the argument. In this example this is not
+        // required, so we just create a new instance of a date_parts.
+        static date_parts pre(boost::gregorian::date) 
+        { 
+            return date_parts(); 
+        }
+
+        // The function post() is called for up-stream conversion of the 
+        // results returned from parsing the right hand side of the rule.
+        // We need to initialize the attribute supplied to the rule with the
+        // values taken from the parsing results.
+        static void post(boost::gregorian::date& d, date_parts const& v)
+        {
+            d = boost::gregorian::date(fusion::at_c<0>(v), fusion::at_c<1>(v)
+              , fusion::at_c<2>(v));
+        }
+    };
+}}}
+
+///////////////////////////////////////////////////////////////////////////////
+namespace client
+{
+    namespace qi = boost::spirit::qi;
+    namespace fusion = boost::fusion;
+
+    typedef fusion::vector<int, int, int> date_parts;
+
+    template <typename Iterator>
+    bool parse_date(Iterator& first, Iterator last, boost::gregorian::date& d)
+    {
+        qi::rule<Iterator, date_parts(), qi::space_type> date =
+            qi::int_ >> '-' >> qi::int_ >> '-' >> qi::int_;
+
+        return phrase_parse(first, last, date, qi::space, d);
+    }
+}
+
+///////////////////////////////////////////////////////////////////////////////
+int main()
+{
+    std::cout << "/////////////////////////////////////////////////////////\n\n";
+    std::cout << "\t\tA date parser for Spirit...\n\n";
+    std::cout << "/////////////////////////////////////////////////////////\n\n";
+
+    std::cout << "Give me a date of the form : year-month-day\n";
+    std::cout << "Type [q or Q] to quit\n\n";
+
+    std::string str;
+    while (getline(std::cin, str))
+    {
+        if (str.empty() || str[0] == 'q' || str[0] == 'Q')
+            break;
+
+        boost::gregorian::date d;
+        std::string::const_iterator iter = str.begin();
+        std::string::const_iterator end = str.end();
+        bool r = client::parse_date(iter, end, d);
+
+        if (r && iter == end)
+        {
+            std::cout << "-------------------------\n";
+            std::cout << "Parsing succeeded\n";
+            std::cout << "got: " << d << std::endl;
+            std::cout << "\n-------------------------\n";
+        }
+        else
+        {
+            std::cout << "-------------------------\n";
+            std::cout << "Parsing failed\n";
+            std::cout << "-------------------------\n";
+        }
+    }
+
+    std::cout << "Bye... :-) \n\n";
+    return 0;
+    return 0;
+}
+
+