implement mp_valid_and_true

test/mp_valid_and_true.cpp

@@ -0,0 +1,48 @@
+// Copyright 2022 Dmitry Arkhipov (grisumbras@gmail.com)
+//
+// 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 <cstddef>
+
+template<class T>
+using has_size_t_difference_type
+    = std::is_same<typename T::difference_type, std::size_t>;
+
+struct X
+{
+};
+
+struct Y
+{
+    using difference_type = int;
+};
+
+struct Z
+{
+    using difference_type = std::size_t;
+};
+
+int main()
+{
+    using boost::mp11::mp_valid_and_true;
+    using boost::mp11::mp_valid_and_true_q;
+    using boost::mp11::mp_quote;
+
+    BOOST_TEST_TRAIT_FALSE((mp_valid_and_true<has_size_t_difference_type, X>));
+    BOOST_TEST_TRAIT_FALSE((mp_valid_and_true<has_size_t_difference_type, Y>));
+    BOOST_TEST_TRAIT_TRUE((mp_valid_and_true<has_size_t_difference_type, Z>));
+
+    using Q_size_t_diff = mp_quote<has_size_t_difference_type>;
+
+    BOOST_TEST_TRAIT_FALSE((mp_valid_and_true_q<Q_size_t_diff, X>));
+    BOOST_TEST_TRAIT_FALSE((mp_valid_and_true_q<Q_size_t_diff, Y>));
+    BOOST_TEST_TRAIT_TRUE((mp_valid_and_true_q<Q_size_t_diff, Z>));
+
+    return boost::report_errors();
+}