add boost on mac

macx64/include/boost/hana/detail/nested_by_fwd.hpp

@@ -0,0 +1,55 @@
+/*!
+@file
+Forward declares `boost::hana::detail::nested_by`.
+
+@copyright Louis Dionne 2013-2017
+Distributed under the Boost Software License, Version 1.0.
+(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
+ */
+
+#ifndef BOOST_HANA_DETAIL_NESTED_BY_FWD_HPP
+#define BOOST_HANA_DETAIL_NESTED_BY_FWD_HPP
+
+#include <boost/hana/config.hpp>
+
+
+BOOST_HANA_NAMESPACE_BEGIN namespace detail {
+    template <typename Algorithm>
+    struct nested_by_t {
+        template <typename Predicate, typename Object>
+        constexpr decltype(auto)
+        operator()(Predicate&& predicate, Object&& object) const;
+
+        template <typename Predicate>
+        constexpr decltype(auto) operator()(Predicate&& predicate) const;
+    };
+
+    //! @ingroup group-details
+    //! Provides a `.by` static constexpr function object.
+    //!
+    //! When creating a binary function object of type `Algorithm` whose
+    //! signature is `Object x Predicate -> Return`, `nested_by<Algorithm>`
+    //! can be used as a base class to `Algorithm`. Doing so will provide a
+    //! static constexpr member called `by`, which has the two following
+    //! signatures:
+    //! @code
+    //!     Predicate x Object -> Return
+    //!     Predicate -> (Object -> Return)
+    //! @endcode
+    //!
+    //! In other words, `nested_by` is a `curry`ed and `flip`ped version of
+    //! `Algorithm`. Note that the function object `Algorithm` must be
+    //! default-constructible, since the algorithm will be called as
+    //! `Algorithm{}(arguments...)`.
+    //!
+    //! @note
+    //! This function object is especially useful because it takes care of
+    //! avoiding ODR violations caused by the nested static constexpr member.
+    template <typename Algorithm>
+    struct nested_by { static constexpr nested_by_t<Algorithm> by{}; };
+
+    template <typename Algorithm>
+    constexpr nested_by_t<Algorithm> nested_by<Algorithm>::by;
+} BOOST_HANA_NAMESPACE_END
+
+#endif // !BOOST_HANA_DETAIL_NESTED_BY_FWD_HPP