1 files changed, 48 insertions, 0 deletions
diff --git a/boost/mp11/detail/mp_copy_if.hpp b/boost/mp11/detail/mp_copy_if.hpp
new file mode 100644
index 0000000000..4edcde090f
--- /dev/null
+++ b/boost/mp11/detail/mp_copy_if.hpp
@@ -0,0 +1,48 @@
+#ifndef BOOST_MP11_DETAIL_MP_COPY_IF_HPP_INCLUDED
+#define BOOST_MP11_DETAIL_MP_COPY_IF_HPP_INCLUDED
+
+//  Copyright 2015-2019 Peter Dimov.
+//
+//  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/mp11/utility.hpp>
+#include <boost/mp11/detail/mp_list.hpp>
+#include <boost/mp11/detail/mp_append.hpp>
+#include <boost/mp11/detail/config.hpp>
+
+namespace boost
+{
+namespace mp11
+{
+
+// mp_copy_if<L, P>
+namespace detail
+{
+
+template<class L, template<class...> class P> struct mp_copy_if_impl
+{
+};
+
+template<template<class...> class L, class... T, template<class...> class P> struct mp_copy_if_impl<L<T...>, P>
+{
+#if BOOST_MP11_WORKAROUND( BOOST_MP11_MSVC, < 1920 )
+    template<class U> struct _f { using type = mp_if<P<U>, mp_list<U>, mp_list<>>; };
+    using type = mp_append<L<>, typename _f<T>::type...>;
+#else
+    template<class U> using _f = mp_if<P<U>, mp_list<U>, mp_list<>>;
+    using type = mp_append<L<>, _f<T>...>;
+#endif
+};
+
+} // namespace detail
+
+template<class L, template<class...> class P> using mp_copy_if = typename detail::mp_copy_if_impl<L, P>::type;
+template<class L, class Q> using mp_copy_if_q = mp_copy_if<L, Q::template fn>;
+
+} // namespace mp11
+} // namespace boost
+
+#endif // #ifndef BOOST_MP11_DETAIL_MP_COPY_IF_HPP_INCLUDED