Add mp_transform_first, second, third

test/mp_transform_third.cpp

@@ -0,0 +1,56 @@
+
+// Copyright 2015, 2017, 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/list.hpp>
+#include <boost/mp11/utility.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+#include <type_traits>
+#include <tuple>
+#include <utility>
+
+struct X1 {};
+struct X2 {};
+struct X3 {};
+struct X4 {};
+
+template<class T> using add_pointer_t = T*;
+using Q_add_pointer = boost::mp11::mp_quote_trait<std::add_pointer>;
+
+int main()
+{
+    using boost::mp11::mp_list;
+    using boost::mp11::mp_transform_third;
+    using boost::mp11::mp_transform_third_q;
+
+    {
+        using L3 = mp_list<X1, X2, X3>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_transform_third<L3, add_pointer_t>, mp_list<X1, X2, X3*>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_transform_third_q<L3, Q_add_pointer>, mp_list<X1, X2, X3*>>));
+
+        using L4 = mp_list<X1, X2, X3, X4>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_transform_third<L4, add_pointer_t>, mp_list<X1, X2, X3*, X4>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_transform_third_q<L4, Q_add_pointer>, mp_list<X1, X2, X3*, X4>>));
+    }
+
+    {
+        using L3 = std::tuple<X1, X2, X3>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_transform_third<L3, add_pointer_t>, std::tuple<X1, X2, X3*>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_transform_third_q<L3, Q_add_pointer>, std::tuple<X1, X2, X3*>>));
+
+        using L4 = std::tuple<X1, X2, X3, X4>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_transform_third<L4, add_pointer_t>, std::tuple<X1, X2, X3*, X4>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_transform_third_q<L4, Q_add_pointer>, std::tuple<X1, X2, X3*, X4>>));
+    }
+
+    return boost::report_errors();
+}