From aa115778121297416a6b925df72727605bb076cb Mon Sep 17 00:00:00 2001
From: Kris Jusiak <kris@jusiak.net>
Date: Tue, 3 Dec 2019 13:08:32 -0700
Subject: [PATCH] :new: [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.
---
 doc/mp11/algorithm.adoc          | 12 +++++++
 include/boost/mp11/algorithm.hpp | 16 ++++++++++
 test/Jamfile                     |  2 ++
 test/mp_unique_if.cpp            | 54 ++++++++++++++++++++++++++++++++
 test/mp_unique_if_q.cpp          | 51 ++++++++++++++++++++++++++++++
 5 files changed, 135 insertions(+)
 create mode 100644 test/mp_unique_if.cpp
 create mode 100644 test/mp_unique_if_q.cpp

diff --git a/doc/mp11/algorithm.adoc b/doc/mp11/algorithm.adoc
index 6dcf9a3..86158be 100644
--- a/doc/mp11/algorithm.adoc
+++ b/doc/mp11/algorithm.adoc
@@ -659,6 +659,18 @@ As `mp_reverse_fold`, but takes a quoted metafunction.
 
 `mp_unique<L>` returns a list of the same form as `L` with the duplicate elements removed.
 
+## mp_unique_if<L, P>
+
+    template<class L> using mp_unique_if = /*...*/;
+
+`mp_unique_if<L, P>` returns a list of the same form as `L` with the duplicate elements removed for which `mp_to_bool<P<T>>` is `mp_true`.
+
+## mp_unique_if<L, Q>
+
+    template<class L, class Q> using mp_unique_if = mp_unique_if<L, Q::template fn>;
+
+As `mp_unique_if`, but takes a quoted metafunction.
+
 ## mp_all_of<L, P>
 
     template<class L, template<class...> class P> using mp_all_of =
diff --git a/include/boost/mp11/algorithm.hpp b/include/boost/mp11/algorithm.hpp
index b8719d6..e874c77 100644
--- a/include/boost/mp11/algorithm.hpp
+++ b/include/boost/mp11/algorithm.hpp
@@ -950,6 +950,22 @@ template<template<class...> class L, class... T> struct mp_unique_impl<L<T...>>
 
 template<class L> using mp_unique = typename detail::mp_unique_impl<L>::type;
 
+namespace detail {
+template <template<class...> class P> struct mp_unique_if_push_back {
+  template<class...> struct impl;
+  template <template<class...> class L, class... Ts, class T>
+  struct impl<L<Ts...>, T> {
+    using type = mp_if<mp_any<P<Ts, T>...>, L<Ts...>, L<Ts..., T>>;
+  };
+  template <class... T> using fn = typename impl<T...>::type;
+};
+} // namespace detail
+
+// mp_unique_if<L, P>
+template <class L, template<class...> class P>
+using mp_unique_if = mp_fold_q<L, mp_clear<L>, detail::mp_unique_if_push_back<P>>;
+template<class L, class Q> using mp_unique_if_q = mp_unique_if<L, Q::template fn>;
+
 // mp_all_of<L, P>
 template<class L, template<class...> class P> using mp_all_of = mp_bool< mp_count_if<L, P>::value == mp_size<L>::value >;
 template<class L, class Q> using mp_all_of_q = mp_all_of<L, Q::template fn>;
diff --git a/test/Jamfile b/test/Jamfile
index e2df961..542221f 100644
--- a/test/Jamfile
+++ b/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 ;
diff --git a/test/mp_unique_if.cpp b/test/mp_unique_if.cpp
new file mode 100644
index 0000000..db527df
--- /dev/null
+++ b/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();
+}
diff --git a/test/mp_unique_if_q.cpp b/test/mp_unique_if_q.cpp
new file mode 100644
index 0000000..55805e3
--- /dev/null
+++ b/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();
+}