Add mp_not_fn

test/mp_not_fn.cpp

@@ -0,0 +1,36 @@
+
+// Copyright 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/core/lightweight_test_trait.hpp>
+#include <type_traits>
+
+template<class T> using is_const_ = std::is_const<T>;
+
+struct Q_is_const
+{
+    template<class T> using fn = std::is_const<T>;
+};
+
+int main()
+{
+    using boost::mp11::mp_not_fn;
+    using boost::mp11::mp_not_fn_q;
+
+    BOOST_TEST_TRAIT_TRUE((mp_not_fn<std::is_const>::fn<void>));
+    BOOST_TEST_TRAIT_FALSE((mp_not_fn<std::is_const>::fn<void const>));
+
+    BOOST_TEST_TRAIT_TRUE((mp_not_fn<is_const_>::fn<void>));
+    BOOST_TEST_TRAIT_FALSE((mp_not_fn<is_const_>::fn<void const>));
+
+    BOOST_TEST_TRAIT_TRUE((mp_not_fn_q<Q_is_const>::fn<void>));
+    BOOST_TEST_TRAIT_FALSE((mp_not_fn_q<Q_is_const>::fn<void const>));
+
+    return boost::report_errors();
+}