🆕 [mp_unique_if] Support for mp_unique with a predicate

Problem:
- `mp_unique` doesn't support custom predicates.

Solution:
- Add `mp_unique_if` and `mp_unique_if_q` which allow to remove duplicates elements with a predicate.

test/Jamfile

@@ -92,6 +92,8 @@ run mp_fold_q.cpp ;
 run mp_reverse_fold.cpp ;
 run mp_reverse_fold_q.cpp ;
 run mp_unique.cpp ;
+run mp_unique_if.cpp ;
+run mp_unique_if_q.cpp ;
 run mp_all_of.cpp ;
 run mp_all_of_q.cpp ;
 run mp_any_of.cpp ;

test/mp_unique_if.cpp

@@ -0,0 +1,54 @@
+//  Copyright 2015 Peter Dimov.
+//  Copyright 2019 Kris Jusiak.
+//
+// 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/algorithm.hpp>
+#include <boost/mp11/list.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+#include <type_traits>
+#include <tuple>
+
+int main()
+{
+    using boost::mp11::mp_list;
+    using boost::mp11::mp_unique_if;
+
+    {
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if<mp_list<>, std::is_same>,mp_list<>>));
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if<mp_list<void>, std::is_same>,mp_list<void>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if<mp_list<void, void>, std::is_same>,mp_list<void>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if<mp_list<void, void, void>, std::is_same>,mp_list<void>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if<mp_list<void, void, void, void>, std::is_same>,mp_list<void>>));
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if<mp_list<void, int>, std::is_same>,mp_list<void, int>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if<mp_list<void, void, void, int, int, int>, std::is_same>,mp_list<void, int>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if<mp_list<void, int, void, int, int, void, int, int, int>, std::is_same>,mp_list<void, int>>));
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if<mp_list<void, int, char[]>, std::is_same>,mp_list<void, int, char[]>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if<mp_list<void, int, char[], void, int, char[], void, int, char[]>, std::is_same>,mp_list<void, int, char[]>>));
+    }
+
+    {
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if<std::tuple<>, std::is_same>,std::tuple<>>));
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if<std::tuple<void>, std::is_same>,std::tuple<void>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if<std::tuple<void, void>, std::is_same>,std::tuple<void>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if<std::tuple<void, void, void>, std::is_same>,std::tuple<void>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if<std::tuple<void, void, void, void>, std::is_same>,std::tuple<void>>));
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if<std::tuple<void, int>, std::is_same>,std::tuple<void, int>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if<std::tuple<void, void, void, int, int, int>, std::is_same>,std::tuple<void, int>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if<std::tuple<void, int, void, int, int, void, int, int, int>, std::is_same>,std::tuple<void, int>>));
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if<std::tuple<void, int, char[]>, std::is_same>,std::tuple<void, int, char[]>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if<std::tuple<void, int, char[], void, int, char[], void, int, char[]>, std::is_same>,std::tuple<void, int, char[]>>));
+    }
+
+    return boost::report_errors();
+}

test/mp_unique_if_q.cpp

@@ -0,0 +1,51 @@
+//  Copyright 2015 Peter Dimov.
+//  Copyright 2019 Kris Jusiak.
+//
+// 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/algorithm.hpp>
+#include <boost/mp11/list.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+#include <type_traits>
+#include <tuple>
+
+struct is_same_size
+{
+    template<class TLhs, class TRhs>
+    struct impl : boost::mp11::mp_bool<sizeof(TLhs) == sizeof(TRhs)> {};
+    template<class TLhs, class TRhs> using fn = typename impl<TLhs, TRhs>::type;
+};
+
+int main()
+{
+    using boost::mp11::mp_list;
+    using boost::mp11::mp_unique_if_q;
+
+    {
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if_q<mp_list<>, is_same_size>, mp_list<>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if_q<mp_list<int>, is_same_size>, mp_list<int>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if_q<mp_list<int, int>, is_same_size>, mp_list<int>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if_q<mp_list<char, bool>, is_same_size>, mp_list<char>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if_q<mp_list<bool, char>, is_same_size>, mp_list<bool>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if_q<mp_list<bool, char, bool>, is_same_size>, mp_list<bool>>));
+        struct foo{};
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if_q<mp_list<char, bool, int, foo>, is_same_size>, mp_list<char, int>>));
+    }
+
+    {
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if_q<std::tuple<>, is_same_size>, std::tuple<>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if_q<std::tuple<int>, is_same_size>, std::tuple<int>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if_q<std::tuple<int, int>, is_same_size>, std::tuple<int>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if_q<std::tuple<char, bool>, is_same_size>, std::tuple<char>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if_q<std::tuple<bool, char>, is_same_size>, std::tuple<bool>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if_q<std::tuple<bool, char, bool>, is_same_size>, std::tuple<bool>>));
+        struct foo{};
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_unique_if_q<std::tuple<char, bool, int, foo>, is_same_size>, std::tuple<char, int>>));
+    }
+
+    return boost::report_errors();
+}