From 353bf4bc09839de7106326d00ed20fda0d48272e Mon Sep 17 00:00:00 2001
From: Dan Marsden <danmarsden@yahoo.co.uk>
Date: Tue, 6 Nov 2007 20:55:58 +0000
Subject: [PATCH] Adding an example of using sequence facade and iterator
 facade.

[SVN r40853]
---
 example/extension/Jamfile    |   4 +-
 example/extension/triple.cpp | 319 +++++++++++++++++++++++++++++++++++
 2 files changed, 322 insertions(+), 1 deletion(-)
 create mode 100644 example/extension/triple.cpp

diff --git a/example/extension/Jamfile b/example/extension/Jamfile
index cf062603..aabe8302 100644
--- a/example/extension/Jamfile
+++ b/example/extension/Jamfile
@@ -13,6 +13,8 @@ import testing ;
 {
     test-suite example :
 
-    [ run test_example.cpp :  :  :  : ] ;
+    [ run test_example.cpp :  :  :  : ]
+    [ run triple.cpp :  :  :  : ]
+    ;
 }
 
diff --git a/example/extension/triple.cpp b/example/extension/triple.cpp
new file mode 100644
index 00000000..ee247439
--- /dev/null
+++ b/example/extension/triple.cpp
@@ -0,0 +1,319 @@
+/*=============================================================================
+    Copyright (c) 2001-2006 Joel de Guzman
+    Copyright (c) 2006 Dan Marsden
+
+    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)
+==============================================================================*/
+
+/*=============================================================================
+    An implementation of a std::pair like triple<T0, T1, T2>
+    We use fusion::sequence_facade and fusion::iterator_facade
+    to make our triple a fully conforming Boost.Fusion random
+    traversal sequence.
+==============================================================================*/
+
+#include <boost/detail/lightweight_test.hpp>
+
+#include <boost/fusion/sequence/sequence_facade.hpp>
+#include <boost/fusion/iterator/iterator_facade.hpp>
+
+#include <boost/fusion/sequence/intrinsic.hpp>
+#include <boost/fusion/iterator.hpp>
+
+#include <boost/fusion/support/category_of.hpp>
+
+#include <boost/mpl/int.hpp>
+#include <boost/mpl/identity.hpp>
+#include <boost/mpl/minus.hpp>
+#include <boost/mpl/assert.hpp>
+
+#include <boost/type_traits/is_const.hpp>
+#include <boost/type_traits/is_same.hpp>
+
+#include <string>
+
+namespace mpl = boost::mpl;
+namespace fusion = boost::fusion;
+
+namespace demo
+{
+    template<typename Seq, int N>
+    struct triple_iterator
+        : fusion::iterator_facade<triple_iterator<Seq, N>, fusion::random_access_traversal_tag>
+    {
+        typedef mpl::int_<N> index;
+        typedef Seq sequence_type;
+
+        triple_iterator(Seq& seq)
+            : seq_(seq) {}
+
+        Seq& seq_;
+
+        template<typename T>
+        struct value_of;
+
+        template<typename Sq>
+        struct value_of<triple_iterator<Sq, 0> >
+            : mpl::identity<typename Sq::t0_type>
+        {};
+
+        template<typename Sq>
+        struct value_of<triple_iterator<Sq, 1> >
+            : mpl::identity<typename Sq::t1_type>
+        {};
+
+        template<typename Sq>
+        struct value_of<triple_iterator<Sq, 2> >
+            : mpl::identity<typename Sq::t2_type>
+        {};
+
+        template<typename T>
+        struct deref;
+
+        template <typename Sq>
+        struct deref<triple_iterator<Sq, 0> >
+        {
+            typedef typename
+                mpl::if_<
+                    boost::is_const<Sq>
+                  , typename Sq::t0_type const&
+                  , typename Sq::t0_type&
+                >::type
+            type;
+
+            static type
+            call(triple_iterator<Sq, 0> const& iter)
+            {
+                return iter.seq_.t0;
+            }
+        };
+
+        template <typename Sq>
+        struct deref<triple_iterator<Sq, 1> >
+        {
+            typedef typename
+                mpl::if_<
+                    boost::is_const<Sq>
+                  , typename Sq::t1_type const&
+                  , typename Sq::t1_type&
+                >::type
+            type;
+
+            static type
+            call(triple_iterator<Sq, 1> const& iter)
+            {
+                return iter.seq_.t1;
+            }
+        };
+
+        template <typename Sq>
+        struct deref<triple_iterator<Sq, 2> >
+        {
+            typedef typename
+                mpl::if_<
+                    boost::is_const<Sq>
+                  , typename Sq::t2_type const&
+                  , typename Sq::t2_type&
+                >::type
+            type;
+
+            static type
+            call(triple_iterator<Sq, 2> const& iter)
+            {
+                return iter.seq_.t2;
+            }
+        };
+
+        template<typename It>
+        struct next
+        {
+            typedef triple_iterator<
+                typename It::sequence_type, It::index::value + 1> type;
+
+            static type call(It const& it)
+            {
+                return type(it.seq_);
+            }
+        };
+
+        template<typename It>
+        struct prior
+        {
+            typedef triple_iterator<
+                typename It::sequence_type, It::index::value - 1> type;
+
+            static type call(It const& it)
+            {
+                return type(it.seq_);
+            }
+        };
+
+        template<typename It1, typename It2>
+        struct distance
+        {
+            typedef typename mpl::minus<typename It2::index, typename It1::index>::type type;
+
+            static type call(It1 const& it1, It2 const& it2)
+            {
+                return type();
+            }
+        };
+
+        template<typename It, typename M>
+        struct advance
+        {
+            typedef triple_iterator<
+                typename It::sequence_type,
+                It::index::value + M::value> type;
+
+            static type call(It const& it)
+            {
+                return type(it.seq_);
+            }
+        };
+    };
+
+    template<typename T0, typename T1, typename T2>
+    struct triple
+        : fusion::sequence_facade<triple<T0, T1, T2>, fusion::random_access_traversal_tag>
+    {
+        triple(T0 const& t0, T1 const& t1, T2 const& t2)
+            : t0(t0), t1(t1), t2(t2)
+        {}
+
+        template<typename Sq>
+        struct begin
+        {
+            typedef demo::triple_iterator<
+                Sq, 0> type;
+
+            static type call(Sq& sq)
+            {
+                return type(sq);
+            }
+        };
+
+        template<typename Sq>
+        struct end
+        {
+            typedef demo::triple_iterator<
+                Sq, 3> type;
+
+            static type call(Sq& sq)
+            {
+                return type(sq);
+            }
+        };
+
+        template<typename Sq>
+        struct size
+            : mpl::int_<3>
+        {};
+
+        template<typename Sq, typename N>
+        struct value_at
+            : value_at<Sq, mpl::int_<N::value> >
+        {};
+
+        template<typename Sq>
+        struct value_at<Sq, mpl::int_<0> >
+        {
+            typedef typename Sq::t0_type type;
+        };
+
+        template<typename Sq>
+        struct value_at<Sq, mpl::int_<1> >
+        {
+            typedef typename Sq::t1_type type;
+        };
+
+        template<typename Sq>
+        struct value_at<Sq, mpl::int_<2> >
+        {
+            typedef typename Sq::t2_type type;
+        };
+
+        template<typename Sq, typename N>
+        struct at
+            : at<Sq, mpl::int_<N::value> >
+        {};
+
+        template<typename Sq>
+        struct at<Sq, mpl::int_<0> >
+        {
+            typedef typename
+                mpl::if_<
+                    boost::is_const<Sq>
+                  , typename Sq::t0_type const&
+                  , typename Sq::t0_type&
+                >::type
+            type;
+
+            static type call(Sq& sq)
+            {
+                return sq.t0;
+            }
+        };
+
+        template<typename Sq>
+        struct at<Sq, mpl::int_<1> >
+        {
+            typedef typename
+                mpl::if_<
+                    boost::is_const<Sq>
+                  , typename Sq::t1_type const&
+                  , typename Sq::t1_type&
+                >::type
+            type;
+
+            static type call(Sq& sq)
+            {
+                return sq.t1;
+            }
+        };
+
+        template<typename Sq>
+        struct at<Sq, mpl::int_<2> >
+        {
+            typedef typename
+                mpl::if_<
+                    boost::is_const<Sq>
+                  , typename Sq::t2_type const&
+                  , typename Sq::t2_type&
+                >::type
+            type;
+
+            static type call(Sq& sq)
+            {
+                return sq.t2;
+            }
+        };
+
+        typedef T0 t0_type;
+        typedef T1 t1_type;
+        typedef T2 t2_type;
+
+        T0 t0;
+        T1 t1;
+        T2 t2;
+    };
+}
+
+int main()
+{
+    typedef demo::triple<int, char, std::string> my_triple;
+    my_triple t(101, 'a', "hello");
+    BOOST_TEST(*fusion::begin(t) == 101);
+    BOOST_TEST(*fusion::next(fusion::begin(t)) == 'a');
+    BOOST_TEST(*fusion::prior(fusion::end(t)) == "hello");
+    BOOST_TEST(fusion::distance(fusion::begin(t), fusion::end(t)) == 3);
+    BOOST_TEST(fusion::size(t) == 3);
+    BOOST_MPL_ASSERT((boost::is_same<int, fusion::result_of::value_at_c<my_triple, 0>::type>));
+    BOOST_MPL_ASSERT((boost::is_same<char, fusion::result_of::value_at_c<my_triple, 1>::type>));
+    BOOST_MPL_ASSERT((boost::is_same<std::string, fusion::result_of::value_at_c<my_triple, 2>::type>));
+    BOOST_TEST(fusion::at_c<0>(t) == 101);
+    BOOST_TEST(fusion::at_c<1>(t) == 'a');
+    BOOST_TEST(fusion::at_c<2>(t) == "hello");
+    return boost::report_errors();
+}