From c1a012ad45c9c2f11eed6250ad1285e6ccaee0b8 Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@gmail.com>
Date: Tue, 16 May 2023 19:46:38 +0300
Subject: [PATCH] Add value list support to mp_take. Refs #53.

---
 include/boost/mp11/algorithm.hpp |  4 +-
 test/Jamfile                     |  1 +
 test/mp_take_2.cpp               | 88 ++++++++++++++++++++++++++++++++
 3 files changed, 91 insertions(+), 2 deletions(-)
 create mode 100644 test/mp_take_2.cpp

diff --git a/include/boost/mp11/algorithm.hpp b/include/boost/mp11/algorithm.hpp
index 82a7aa9..7d7e579 100644
--- a/include/boost/mp11/algorithm.hpp
+++ b/include/boost/mp11/algorithm.hpp
@@ -470,8 +470,8 @@ struct mp_take_c_impl<N, L<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T...>, typen
 
 } // namespace detail
 
-template<class L, std::size_t N> using mp_take_c = typename detail::mp_take_c_impl<N, L>::type;
-template<class L, class N> using mp_take = typename detail::mp_take_c_impl<std::size_t{ N::value }, L>::type;
+template<class L, std::size_t N> using mp_take_c = mp_assign<L, typename detail::mp_take_c_impl<N, mp_rename<L, mp_list>>::type>;
+template<class L, class N> using mp_take = mp_take_c<L, std::size_t{ N::value }>;
 
 // mp_back<L>
 template<class L> using mp_back = mp_at_c<L, mp_size<L>::value - 1>;
diff --git a/test/Jamfile b/test/Jamfile
index 665354b..79c4eaf 100644
--- a/test/Jamfile
+++ b/test/Jamfile
@@ -97,6 +97,7 @@ run mp_at.cpp ;
 run mp_at_2.cpp ;
 run mp_at_sf.cpp : : : <toolset>gcc-4.7:<warnings>all ;
 run mp_take.cpp ;
+run mp_take_2.cpp ;
 run mp_replace.cpp ;
 run mp_replace_if.cpp ;
 run mp_replace_if_q.cpp ;
diff --git a/test/mp_take_2.cpp b/test/mp_take_2.cpp
new file mode 100644
index 0000000..56adc5b
--- /dev/null
+++ b/test/mp_take_2.cpp
@@ -0,0 +1,88 @@
+// Copyright 2023 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/mp11/algorithm.hpp>
+#include <boost/mp11/list.hpp>
+#include <boost/mp11/integral.hpp>
+
+#if !defined(BOOST_MP11_HAS_TEMPLATE_AUTO)
+
+#pragma message("Test skipped because BOOST_MP11_HAS_TEMPLATE_AUTO is not defined")
+int main() {}
+
+#else
+
+#include <boost/core/lightweight_test_trait.hpp>
+
+template<auto... A> struct V1 {};
+template<int... I> struct V2 {};
+
+int main()
+{
+    using boost::mp11::mp_list;
+    using boost::mp11::mp_take;
+    using boost::mp11::mp_take_c;
+    using boost::mp11::mp_size_t;
+
+    {
+        using L1 = V1<>;
+
+        BOOST_TEST_TRAIT_SAME(mp_take_c<L1, 0>, L1);
+        BOOST_TEST_TRAIT_SAME(mp_take<L1, mp_size_t<0>>, L1);
+
+        using L2 = V1<false, 0, true, 1, std::size_t(2)>;
+
+        BOOST_TEST_TRAIT_SAME(mp_take_c<L2, 0>, V1<>);
+        BOOST_TEST_TRAIT_SAME(mp_take_c<L2, 1>, V1<false>);
+        BOOST_TEST_TRAIT_SAME(mp_take_c<L2, 2>, V1<false, 0>);
+        BOOST_TEST_TRAIT_SAME(mp_take_c<L2, 3>, V1<false, 0, true>);
+        BOOST_TEST_TRAIT_SAME(mp_take_c<L2, 4>, V1<false, 0, true, 1>);
+        BOOST_TEST_TRAIT_SAME(mp_take_c<L2, 5>, V1<false, 0, true, 1, std::size_t(2)>);
+
+        BOOST_TEST_TRAIT_SAME(mp_take<L2, mp_size_t<0>>, V1<>);
+        BOOST_TEST_TRAIT_SAME(mp_take<L2, mp_size_t<1>>, V1<false>);
+        BOOST_TEST_TRAIT_SAME(mp_take<L2, mp_size_t<2>>, V1<false, 0>);
+        BOOST_TEST_TRAIT_SAME(mp_take<L2, mp_size_t<3>>, V1<false, 0, true>);
+        BOOST_TEST_TRAIT_SAME(mp_take<L2, mp_size_t<4>>, V1<false, 0, true, 1>);
+        BOOST_TEST_TRAIT_SAME(mp_take<L2, mp_size_t<5>>, V1<false, 0, true, 1, std::size_t(2)>);
+    }
+
+    {
+        using L1 = V2<>;
+
+        BOOST_TEST_TRAIT_SAME(mp_take_c<L1, 0>, L1);
+        BOOST_TEST_TRAIT_SAME(mp_take<L1, mp_size_t<0>>, L1);
+
+        using L2 = V2<1, 2, 3, 4, 5>;
+
+        BOOST_TEST_TRAIT_SAME(mp_take_c<L2, 0>, V2<>);
+        BOOST_TEST_TRAIT_SAME(mp_take_c<L2, 1>, V2<1>);
+        BOOST_TEST_TRAIT_SAME(mp_take_c<L2, 2>, V2<1, 2>);
+        BOOST_TEST_TRAIT_SAME(mp_take_c<L2, 3>, V2<1, 2, 3>);
+        BOOST_TEST_TRAIT_SAME(mp_take_c<L2, 4>, V2<1, 2, 3, 4>);
+        BOOST_TEST_TRAIT_SAME(mp_take_c<L2, 5>, V2<1, 2, 3, 4, 5>);
+
+        BOOST_TEST_TRAIT_SAME(mp_take<L2, mp_size_t<0>>, V2<>);
+        BOOST_TEST_TRAIT_SAME(mp_take<L2, mp_size_t<1>>, V2<1>);
+        BOOST_TEST_TRAIT_SAME(mp_take<L2, mp_size_t<2>>, V2<1, 2>);
+        BOOST_TEST_TRAIT_SAME(mp_take<L2, mp_size_t<3>>, V2<1, 2, 3>);
+        BOOST_TEST_TRAIT_SAME(mp_take<L2, mp_size_t<4>>, V2<1, 2, 3, 4>);
+        BOOST_TEST_TRAIT_SAME(mp_take<L2, mp_size_t<5>>, V2<1, 2, 3, 4, 5>);
+    }
+
+    using boost::mp11::mp_iota_c;
+    using boost::mp11::mp_rename_v;
+
+    {
+        using L1 = mp_rename_v<mp_iota_c<71>, V1>;
+        using L2 = mp_rename_v<mp_iota_c<72>, V1>;
+
+        BOOST_TEST_TRAIT_SAME(mp_take_c<L2, 72>, L2);
+        BOOST_TEST_TRAIT_SAME(mp_take_c<L2, 71>, L1);
+    }
+
+    return boost::report_errors();
+}
+
+#endif