Initial move from Spirit CVS

[SVN r34896]

include/boost/fusion/algorithm/iteration/detail/fold.hpp

@@ -0,0 +1,99 @@
+/*=============================================================================
+    Copyright (c) 2001-2006 Joel de Guzman
+
+    Use, modification and distribution is subject to 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)
+==============================================================================*/
+#if !defined(FUSION_FOLD_05052005_1211)
+#define FUSION_FOLD_05052005_1211
+
+#include <boost/mpl/bool.hpp>
+#include <boost/mpl/apply.hpp>
+#include <boost/mpl/identity.hpp>
+#include <boost/fusion/iterator/equal_to.hpp>
+#include <boost/fusion/sequence/intrinsic/begin.hpp>
+#include <boost/fusion/sequence/intrinsic/end.hpp>
+#include <boost/fusion/iterator/deref.hpp>
+#include <boost/fusion/iterator/value_of.hpp>
+#include <boost/fusion/iterator/next.hpp>
+
+namespace boost { namespace fusion { namespace detail
+{
+    // Unary arguments version
+
+    template <typename F>
+    struct apply_fold_result
+    {
+        template <typename Value, typename State>
+        struct apply
+        {
+            typedef typename F::template result<Value, State>::type type;
+        };
+    };
+
+    template <typename Iterator, typename State, typename F>
+    struct fold_apply
+        : mpl::apply<apply_fold_result<F>, typename result_of::value_of<Iterator>::type, State>
+    {};
+
+    template <typename First, typename Last, typename State, typename F>
+    struct static_fold;
+
+    template <typename First, typename Last, typename State, typename F>
+    struct next_result_of_fold
+    {
+        typedef typename
+            static_fold<
+                typename result_of::next<First>::type
+              , Last
+              , typename fold_apply<First, State, F>::type
+              , F
+            >::type
+        type;
+    };
+
+    template <typename First, typename Last, typename State, typename F>
+    struct static_fold
+    {
+        typedef typename
+            mpl::if_<
+                result_of::equal_to<First, Last>
+              , mpl::identity<State>
+              , next_result_of_fold<First, Last, State, F>
+            >::type
+        result;
+
+        typedef typename result::type type;
+    };
+
+    // terminal case
+    template <typename First, typename Last, typename State, typename F>
+    inline State const&
+    fold(First const&, Last const&, State const& state, F const&, mpl::true_)
+    {
+        return state;
+    }
+
+    // non-terminal case
+    template <typename First, typename Last, typename State, typename F>
+    inline typename static_fold<First, Last, State, F>::type
+    fold(
+        First const& first
+      , Last const& last
+      , State const& state
+      , F const& f
+      , mpl::false_)
+    {
+        return detail::fold(
+            fusion::next(first)
+          , last
+          , f(*first, state)
+          , f
+          , result_of::equal_to<typename result_of::next<First>::type, Last>()
+        );
+    }
+}}}
+
+#endif
+