1 files changed, 138 insertions, 0 deletions
diff --git a/src/boost/libs/phoenix/example/invert.cpp b/src/boost/libs/phoenix/example/invert.cpp
new file mode 100644
index 00000000..3c5e64f0
--- /dev/null
+++ b/src/boost/libs/phoenix/example/invert.cpp
@@ -0,0 +1,138 @@
+/*==============================================================================
+    Copyright (c) 2005-2010 Joel de Guzman
+    Copyright (c) 2010 Thomas Heller
+
+    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)
+==============================================================================*/
+
+#include <boost/phoenix/phoenix.hpp>
+#include <boost/proto/proto.hpp>
+#include <boost/proto/debug.hpp>
+
+namespace phoenix = boost::phoenix;
+namespace proto = boost::proto;
+
+using phoenix::evaluator;
+
+#ifdef _MSC_VER
+// redifining evaluator, this is because MSVC chokes on function types like:
+// F(G(...))
+#define evaluator(A0, A1) proto::call<phoenix::evaluator(A0, A1)>
+#endif
+
+struct invert_actions
+{
+    template <typename Rule>
+    struct when
+        : proto::nary_expr<
+              proto::_
+            , proto::vararg<
+                  proto::when<proto::_, evaluator(proto::_, phoenix::_context)>
+              >
+          >
+    {};
+};
+
+template <>
+struct invert_actions::when<phoenix::rule::plus>
+    : proto::call<
+        phoenix::functional::make_minus(
+            evaluator(proto::_left, phoenix::_context)
+          , evaluator(proto::_right, phoenix::_context)
+        )
+    >
+{};
+
+template <>
+struct invert_actions::when<phoenix::rule::minus>
+    : proto::call<
+        phoenix::functional::make_plus(
+            evaluator(proto::_left, phoenix::_context)
+          , evaluator(proto::_right, phoenix::_context)
+        )
+    >
+{};
+
+template <>
+struct invert_actions::when<phoenix::rule::multiplies>
+    : proto::call<
+        phoenix::functional::make_divides(
+            evaluator(proto::_left, phoenix::_context)
+          , evaluator(proto::_right, phoenix::_context)
+        )
+    >
+{};
+
+template <>
+struct invert_actions::when<phoenix::rule::divides>
+    : proto::call<
+        phoenix::functional::make_multiplies(
+            evaluator(proto::_left, phoenix::_context)
+          , evaluator(proto::_right, phoenix::_context)
+        )
+    >
+{};
+
+#ifdef _MSC_VER
+#undef evaluator
+#endif
+
+template <typename Expr>
+void print_expr(Expr const & expr)
+{
+    std::cout << "before inversion:\n";
+    proto::display_expr(expr);
+    std::cout << "after inversion:\n";
+    proto::display_expr(
+        phoenix::eval(
+            expr
+          , phoenix::context(
+                phoenix::nothing
+              , invert_actions()
+            )
+        )
+    );
+    std::cout << "\n";
+}
+
+template <typename Expr>
+typename
+    boost::phoenix::result_of::eval<
+        Expr const&
+      , phoenix::result_of::make_context<
+            phoenix::result_of::make_env<>::type
+          , invert_actions
+        >::type
+    >::type
+invert(Expr const & expr)
+{
+    return 
+        phoenix::eval(
+            expr
+          , phoenix::make_context(
+                phoenix::make_env()
+              , invert_actions()
+            )
+        );
+}
+
+int main()
+{
+    using phoenix::placeholders::_1;
+    using phoenix::placeholders::_2;
+    using phoenix::placeholders::_3;
+    using phoenix::placeholders::_4;
+
+    print_expr(_1);
+    print_expr(_1 + _2);
+    print_expr(_1 + _2 - _3);
+    print_expr(_1 * _2);
+    print_expr(_1 * _2 / _3);
+    print_expr(_1 * _2 + _3);
+    print_expr(_1 * _2 - _3);
+    print_expr(if_(_1 * _4)[_2 - _3]);
+
+    print_expr(_1 * invert(_2 - _3));
+}
+