1 files changed, 56 insertions, 0 deletions
diff --git a/boost/spirit/home/x3/support/traits/variant_has_substitute.hpp b/boost/spirit/home/x3/support/traits/variant_has_substitute.hpp
new file mode 100644
index 0000000000..d0dfb49b8d
--- /dev/null
+++ b/boost/spirit/home/x3/support/traits/variant_has_substitute.hpp
@@ -0,0 +1,56 @@
+/*=============================================================================
+    Copyright (c) 2001-2014 Joel de Guzman
+    http://spirit.sourceforge.net/
+
+    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)
+=============================================================================*/
+#if !defined(BOOST_SPIRIT_X3_VARIANT_HAS_SUBSTITUTE_APR_18_2014_925AM)
+#define BOOST_SPIRIT_X3_VARIANT_HAS_SUBSTITUTE_APR_18_2014_925AM
+
+#if defined(_MSC_VER)
+#pragma once
+#endif
+
+#include <boost/spirit/home/x3/support/traits/is_substitute.hpp>
+
+namespace boost { namespace spirit { namespace x3 { namespace traits
+{
+    template <typename Variant, typename Attribute>
+    struct variant_has_substitute_impl
+    {
+        // Find a type from the variant that can be a substitute for Attribute.
+        // return true_ if one is found, else false_
+
+        typedef Variant variant_type;
+        typedef typename variant_type::types types;
+        typedef typename mpl::end<types>::type end;
+
+        typedef typename
+            mpl::find_if<types, is_same<mpl::_1, Attribute>>::type
+        iter_1;
+
+        typedef typename
+            mpl::eval_if<
+                is_same<iter_1, end>,
+                mpl::find_if<types, traits::is_substitute<mpl::_1, Attribute>>,
+                mpl::identity<iter_1>
+            >::type
+        iter;
+
+        typedef mpl::not_<is_same<iter, end>> type;
+    };
+
+    template <typename Variant, typename Attribute>
+    struct variant_has_substitute
+        : variant_has_substitute_impl<Variant, Attribute>::type {};
+
+    template <typename Attribute>
+    struct variant_has_substitute<unused_type, Attribute> : mpl::true_ {};
+
+    template <typename Attribute>
+    struct variant_has_substitute<unused_type const, Attribute> : mpl::true_ {};
+
+}}}}
+
+#endif