From 570acee866c6b39df2026f1e3387f5754fb0c7e5 Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@gmail.com>
Date: Sun, 14 May 2023 19:45:09 +0300
Subject: [PATCH] Add mp_value; enable mp_rename on value lists. Refs #53.

---
 include/boost/mp11/detail/config.hpp    | 11 +++++++
 include/boost/mp11/detail/mp_rename.hpp | 20 ++++++++---
 include/boost/mp11/detail/mp_value.hpp  | 25 ++++++++++++++
 include/boost/mp11/integral.hpp         |  1 +
 test/Jamfile                            |  2 ++
 test/mp_rename_2.cpp                    | 44 +++++++++++++++++++++++++
 test/mp_value.cpp                       | 40 ++++++++++++++++++++++
 7 files changed, 139 insertions(+), 4 deletions(-)
 create mode 100644 include/boost/mp11/detail/mp_value.hpp
 create mode 100644 test/mp_rename_2.cpp
 create mode 100644 test/mp_value.cpp

diff --git a/include/boost/mp11/detail/config.hpp b/include/boost/mp11/detail/config.hpp
index 764bd59..44686c7 100644
--- a/include/boost/mp11/detail/config.hpp
+++ b/include/boost/mp11/detail/config.hpp
@@ -123,6 +123,17 @@
 # endif
 #endif
 
+// BOOST_MP11_HAS_TEMPLATE_AUTO
+
+#if defined(__cpp_nontype_template_parameter_auto) && __cpp_nontype_template_parameter_auto >= 201606L
+# define BOOST_MP11_HAS_TEMPLATE_AUTO
+#endif
+
+#if BOOST_MP11_WORKAROUND( BOOST_MP11_MSVC, < 1920 )
+// mp_value<0> is bool, mp_value<-1L> is int, etc
+# undef BOOST_MP11_HAS_TEMPLATE_AUTO
+#endif
+
 // BOOST_MP11_DEPRECATED(msg)
 
 #if BOOST_MP11_WORKAROUND( BOOST_MP11_CLANG, < 304 )
diff --git a/include/boost/mp11/detail/mp_rename.hpp b/include/boost/mp11/detail/mp_rename.hpp
index 5af6fc4..dde8f6f 100644
--- a/include/boost/mp11/detail/mp_rename.hpp
+++ b/include/boost/mp11/detail/mp_rename.hpp
@@ -1,7 +1,7 @@
 #ifndef BOOST_MP11_DETAIL_MP_RENAME_HPP_INCLUDED
 #define BOOST_MP11_DETAIL_MP_RENAME_HPP_INCLUDED
 
-//  Copyright 2015-2021 Peter Dimov.
+//  Copyright 2015-2023 Peter Dimov.
 //
 //  Distributed under the Boost Software License, Version 1.0.
 //
@@ -9,6 +9,8 @@
 //  http://www.boost.org/LICENSE_1_0.txt
 
 #include <boost/mp11/detail/mp_defer.hpp>
+#include <boost/mp11/detail/mp_value.hpp>
+#include <boost/mp11/detail/config.hpp>
 
 namespace boost
 {
@@ -19,21 +21,31 @@ namespace mp11
 namespace detail
 {
 
-template<class A, template<class...> class B> struct mp_rename_impl
+template<class L, template<class...> class B> struct mp_rename_impl
 {
 // An error "no type named 'type'" here means that the first argument to mp_rename is not a list
 };
 
-template<template<class...> class A, class... T, template<class...> class B> struct mp_rename_impl<A<T...>, B>: mp_defer<B, T...>
+template<template<class...> class L, class... T, template<class...> class B> struct mp_rename_impl<L<T...>, B>: mp_defer<B, T...>
 {
 };
 
+#if defined(BOOST_MP11_HAS_TEMPLATE_AUTO)
+
+template<template<auto...> class L, auto... A, template<class...> class B> struct mp_rename_impl<L<A...>, B>: mp_defer<B, mp_value<A>...>
+{
+};
+
+#endif
+
 } // namespace detail
 
-template<class A, template<class...> class B> using mp_rename = typename detail::mp_rename_impl<A, B>::type;
+template<class L, template<class...> class B> using mp_rename = typename detail::mp_rename_impl<L, B>::type;
 
+// mp_apply<F, L>
 template<template<class...> class F, class L> using mp_apply = typename detail::mp_rename_impl<L, F>::type;
 
+// mp_apply_q<Q, L>
 template<class Q, class L> using mp_apply_q = typename detail::mp_rename_impl<L, Q::template fn>::type;
 
 } // namespace mp11
diff --git a/include/boost/mp11/detail/mp_value.hpp b/include/boost/mp11/detail/mp_value.hpp
new file mode 100644
index 0000000..d0e5982
--- /dev/null
+++ b/include/boost/mp11/detail/mp_value.hpp
@@ -0,0 +1,25 @@
+#ifndef BOOST_MP11_DETAIL_MP_VALUE_HPP_INCLUDED
+#define BOOST_MP11_DETAIL_MP_VALUE_HPP_INCLUDED
+
+// Copyright 2023 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/mp11/detail/config.hpp>
+#include <type_traits>
+
+#if defined(BOOST_MP11_HAS_TEMPLATE_AUTO)
+
+namespace boost
+{
+namespace mp11
+{
+
+template<auto A> using mp_value = std::integral_constant<decltype(A), A>;
+
+} // namespace mp11
+} // namespace boost
+
+#endif // #if defined(BOOST_MP11_HAS_TEMPLATE_AUTO)
+
+#endif // #ifndef BOOST_MP11_DETAIL_MP_VALUE_HPP_INCLUDED
diff --git a/include/boost/mp11/integral.hpp b/include/boost/mp11/integral.hpp
index 0671673..1b4fea3 100644
--- a/include/boost/mp11/integral.hpp
+++ b/include/boost/mp11/integral.hpp
@@ -9,6 +9,7 @@
 //  http://www.boost.org/LICENSE_1_0.txt
 
 #include <boost/mp11/version.hpp>
+#include <boost/mp11/detail/mp_value.hpp>
 #include <type_traits>
 #include <cstddef>
 
diff --git a/test/Jamfile b/test/Jamfile
index 4a308a8..05ea4f5 100644
--- a/test/Jamfile
+++ b/test/Jamfile
@@ -34,6 +34,7 @@ run mp_third.cpp ;
 run mp_push_front.cpp ;
 run mp_push_back.cpp ;
 run mp_rename.cpp ;
+run mp_rename_2.cpp ;
 run mp_append.cpp ;
 run mp_append_2.cpp ;
 run mp_append_sf.cpp ;
@@ -133,6 +134,7 @@ run mp_join.cpp ;
 
 # integral
 run integral.cpp ;
+run mp_value.cpp ;
 
 # utility
 run mp_identity.cpp ;
diff --git a/test/mp_rename_2.cpp b/test/mp_rename_2.cpp
new file mode 100644
index 0000000..70c187f
--- /dev/null
+++ b/test/mp_rename_2.cpp
@@ -0,0 +1,44 @@
+// Copyright 2015-2023 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/mp11/list.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/mp11/integral.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+
+template<auto... T> struct L {};
+
+int main()
+{
+    using boost::mp11::mp_list;
+    using boost::mp11::mp_rename;
+    using boost::mp11::mp_true;
+    using boost::mp11::mp_false;
+    using boost::mp11::mp_int;
+    using boost::mp11::mp_size_t;
+
+    BOOST_TEST_TRAIT_SAME(mp_rename<L<>, mp_list>, mp_list<>);
+
+    BOOST_TEST_TRAIT_SAME(mp_rename<L<false>, mp_list>, mp_list<mp_false>);
+    BOOST_TEST_TRAIT_SAME(mp_rename<L<true>, mp_list>, mp_list<mp_true>);
+
+    BOOST_TEST_TRAIT_SAME(mp_rename<L<0>, mp_list>, mp_list<mp_int<0>>);
+    BOOST_TEST_TRAIT_SAME(mp_rename<L<-1>, mp_list>, mp_list<mp_int<-1>>);
+
+    BOOST_TEST_TRAIT_SAME(mp_rename<L<std::size_t(0)>, mp_list>, mp_list<mp_size_t<0>>);
+    BOOST_TEST_TRAIT_SAME(mp_rename<L<std::size_t(1)>, mp_list>, mp_list<mp_size_t<1>>);
+
+    BOOST_TEST_TRAIT_SAME(mp_rename<L<false, 0, std::size_t(0)>, mp_list>, mp_list<mp_false, mp_int<0>, mp_size_t<0>>);
+
+    return boost::report_errors();
+}
+
+#endif
diff --git a/test/mp_value.cpp b/test/mp_value.cpp
new file mode 100644
index 0000000..a81854d
--- /dev/null
+++ b/test/mp_value.cpp
@@ -0,0 +1,40 @@
+// Copyright 2023 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#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>
+#include <type_traits>
+#include <cstddef>
+
+int main()
+{
+    using boost::mp11::mp_value;
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_value<false>, std::integral_constant<bool, false>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_value<true>, std::integral_constant<bool, true>>));
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_value<'a'>, std::integral_constant<char, 'a'>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_value<'0'>, std::integral_constant<char, '0'>>));
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_value<0>, std::integral_constant<int, 0>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_value<-1>, std::integral_constant<int, -1>>));
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_value<0L>, std::integral_constant<long, 0>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_value<-1L>, std::integral_constant<long, -1>>));
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_value<0u>, std::integral_constant<unsigned, 0>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_value<1u>, std::integral_constant<unsigned, 1>>));
+
+    return boost::report_errors();
+}
+
+#endif