Add BOOST_PP_VA_OPT implementation

include/boost/preprocessor/facilities/va_opt.hpp

@@ -0,0 +1,29 @@
+# /* **************************************************************************
+#  *                                                                          *
+#  *     (C) Copyright Edward Diener 2019.
+#  *     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)
+#  *                                                                          *
+#  ************************************************************************** */
+#
+# /* See http://www.boost.org for most recent version. */
+#
+# ifndef BOOST_PREPROCESSOR_FACILITIES_VA_OPT_HPP
+# define BOOST_PREPROCESSOR_FACILITIES_VA_OPT_HPP
+# include <boost/preprocessor/variadic/has_opt.hpp>
+# if BOOST_PP_VARIADIC_HAS_OPT()
+# include <boost/preprocessor/control/iif.hpp>
+# include <boost/preprocessor/facilities/check_empty.hpp>
+# include <boost/preprocessor/tuple/rem.hpp>
+# define BOOST_PP_VA_OPT(rdata,rempty,...) \
+    BOOST_PP_TUPLE_REM() \
+    BOOST_PP_IIF \
+        ( \
+        BOOST_PP_CHECK_EMPTY(__VA_ARGS__), \
+        rempty, \
+        rdata \
+        } \
+/**?
+# endif /* BOOST_PP_VARIADIC_HAS_OPT() */
+# endif /* BOOST_PREPROCESSOR_FACILITIES_VA_OPT_HPP */