1 files changed, 50 insertions, 0 deletions
diff --git a/boost/metaparse/v1/look_ahead.hpp b/boost/metaparse/v1/look_ahead.hpp
new file mode 100644
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+++ b/boost/metaparse/v1/look_ahead.hpp
@@ -0,0 +1,50 @@
+#ifndef BOOST_METAPARSE_V1_LOOK_AHEAD_HPP
+#define BOOST_METAPARSE_V1_LOOK_AHEAD_HPP
+
+// Copyright Abel Sinkovics (abel@sinkovics.hu)   2011.
+// 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/metaparse/v1/is_error.hpp>
+#include <boost/metaparse/v1/accept.hpp>
+#include <boost/metaparse/v1/get_result.hpp>
+
+#include <boost/mpl/eval_if.hpp>
+
+namespace boost
+{
+  namespace metaparse
+  {
+    namespace v1
+    {
+      template <class P>
+      struct look_ahead
+      {
+      private:
+        template <class S, class Pos>
+        struct no_error :
+          accept<
+            typename get_result<typename P::template apply<S, Pos> >::type,
+            S,
+            Pos
+          >
+        {};
+      public:
+        typedef look_ahead type;
+        
+        template <class S, class Pos>
+        struct apply :
+          boost::mpl::eval_if<
+            typename is_error<typename P::template apply<S, Pos> >::type,
+            typename P::template apply<S, Pos>,
+            no_error<S, Pos>
+          >
+        {};
+      };
+    }
+  }
+}
+
+#endif
+