From 79f8c574f3426bb4137b934d396509cafd03c96a Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@pdimov.com>
Date: Sat, 18 Mar 2017 19:58:38 +0200
Subject: [PATCH] Add mp_replace_{front,first,second,third}

---
 include/boost/mp11/list.hpp | 48 ++++++++++++++++++++++
 test/Jamfile.v2             |  3 ++
 test/mp_replace_front.cpp   | 80 +++++++++++++++++++++++++++++++++++++
 test/mp_replace_second.cpp  | 62 ++++++++++++++++++++++++++++
 test/mp_replace_third.cpp   | 48 ++++++++++++++++++++++
 5 files changed, 241 insertions(+)
 create mode 100644 test/mp_replace_front.cpp
 create mode 100644 test/mp_replace_second.cpp
 create mode 100644 test/mp_replace_third.cpp

diff --git a/include/boost/mp11/list.hpp b/include/boost/mp11/list.hpp
index bb319d6..216d8c4 100644
--- a/include/boost/mp11/list.hpp
+++ b/include/boost/mp11/list.hpp
@@ -170,6 +170,54 @@ template<template<class...> class L1, class... T1, template<class...> class L2,
 
 template<class... L> using mp_append = typename detail::mp_append_impl<L...>::type;
 
+// mp_replace_front<L, T>
+namespace detail
+{
+
+template<class L, class T> struct mp_replace_front_impl;
+
+template<template<class...> class L, class U1, class... U, class T> struct mp_replace_front_impl<L<U1, U...>, T>
+{
+    using type = L<T, U...>;
+};
+
+} // namespace detail
+
+template<class L, class T> using mp_replace_front = typename detail::mp_replace_front_impl<L, T>::type;
+
+// mp_replace_first<L, T>
+template<class L, class T> using mp_replace_first = typename detail::mp_replace_front_impl<L, T>::type;
+
+// mp_replace_second<L, T>
+namespace detail
+{
+
+template<class L, class T> struct mp_replace_second_impl;
+
+template<template<class...> class L, class U1, class U2, class... U, class T> struct mp_replace_second_impl<L<U1, U2, U...>, T>
+{
+    using type = L<U1, T, U...>;
+};
+
+} // namespace detail
+
+template<class L, class T> using mp_replace_second = typename detail::mp_replace_second_impl<L, T>::type;
+
+// mp_replace_third<L, T>
+namespace detail
+{
+
+template<class L, class T> struct mp_replace_third_impl;
+
+template<template<class...> class L, class U1, class U2, class U3, class... U, class T> struct mp_replace_third_impl<L<U1, U2, U3, U...>, T>
+{
+    using type = L<U1, U2, T, U...>;
+};
+
+} // namespace detail
+
+template<class L, class T> using mp_replace_third = typename detail::mp_replace_third_impl<L, T>::type;
+
 } // namespace mp11
 } // namespace boost
 
diff --git a/test/Jamfile.v2 b/test/Jamfile.v2
index 29c916b..14d21b0 100644
--- a/test/Jamfile.v2
+++ b/test/Jamfile.v2
@@ -25,6 +25,9 @@ run mp_push_front.cpp : : : $(REQ) ;
 run mp_push_back.cpp : : : $(REQ) ;
 run mp_rename.cpp : : : $(REQ) ;
 run mp_append.cpp : : : $(REQ) ;
+run mp_replace_front.cpp : : : $(REQ) ;
+run mp_replace_second.cpp : : : $(REQ) ;
+run mp_replace_third.cpp : : : $(REQ) ;
 
 # algorithm
 run mp_assign.cpp : : : $(REQ) ;
diff --git a/test/mp_replace_front.cpp b/test/mp_replace_front.cpp
new file mode 100644
index 0000000..7d656d1
--- /dev/null
+++ b/test/mp_replace_front.cpp
@@ -0,0 +1,80 @@
+
+//  Copyright 2015, 2017 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/algorithm.hpp>
+#include <boost/mp11/list.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+#include <type_traits>
+#include <tuple>
+#include <utility>
+
+struct X1 {};
+struct X2 {};
+struct X3 {};
+struct X4 {};
+
+int main()
+{
+    using boost::mp11::mp_list;
+    using boost::mp11::mp_replace_front;
+    using boost::mp11::mp_replace_first;
+
+    {
+        using L1 = mp_list<X1>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_front<L1, void>, mp_list<void>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_first<L1, void>, mp_list<void>>));
+
+        using L2 = mp_list<X1, X2>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_front<L2, void>, mp_list<void, X2>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_first<L2, void>, mp_list<void, X2>>));
+
+        using L3 = mp_list<X1, X2, X3>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_front<L3, void>, mp_list<void, X2, X3>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_first<L3, void>, mp_list<void, X2, X3>>));
+
+        using L4 = mp_list<X1, X2, X3, X4>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_front<L4, void>, mp_list<void, X2, X3, X4>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_first<L4, void>, mp_list<void, X2, X3, X4>>));
+    }
+
+    {
+        using L1 = std::tuple<X1>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_front<L1, void>, std::tuple<void>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_first<L1, void>, std::tuple<void>>));
+
+        using L2 = std::tuple<X1, X2>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_front<L2, void>, std::tuple<void, X2>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_first<L2, void>, std::tuple<void, X2>>));
+
+        using L3 = std::tuple<X1, X2, X3>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_front<L3, void>, std::tuple<void, X2, X3>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_first<L3, void>, std::tuple<void, X2, X3>>));
+
+        using L4 = std::tuple<X1, X2, X3, X4>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_front<L4, void>, std::tuple<void, X2, X3, X4>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_first<L4, void>, std::tuple<void, X2, X3, X4>>));
+    }
+
+    {
+        using L2 = std::pair<X1, X2>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_front<L2, void>, std::pair<void, X2>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_first<L2, void>, std::pair<void, X2>>));
+    }
+
+    return boost::report_errors();
+}
diff --git a/test/mp_replace_second.cpp b/test/mp_replace_second.cpp
new file mode 100644
index 0000000..d7f1e86
--- /dev/null
+++ b/test/mp_replace_second.cpp
@@ -0,0 +1,62 @@
+
+//  Copyright 2015, 2017 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/algorithm.hpp>
+#include <boost/mp11/list.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+#include <type_traits>
+#include <tuple>
+#include <utility>
+
+struct X1 {};
+struct X2 {};
+struct X3 {};
+struct X4 {};
+
+int main()
+{
+    using boost::mp11::mp_list;
+    using boost::mp11::mp_replace_second;
+
+    {
+        using L2 = mp_list<X1, X2>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_second<L2, void>, mp_list<X1, void>>));
+
+        using L3 = mp_list<X1, X2, X3>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_second<L3, void>, mp_list<X1, void, X3>>));
+
+        using L4 = mp_list<X1, X2, X3, X4>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_second<L4, void>, mp_list<X1, void, X3, X4>>));
+    }
+
+    {
+        using L2 = std::tuple<X1, X2>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_second<L2, void>, std::tuple<X1, void>>));
+
+        using L3 = std::tuple<X1, X2, X3>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_second<L3, void>, std::tuple<X1, void, X3>>));
+
+        using L4 = std::tuple<X1, X2, X3, X4>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_second<L4, void>, std::tuple<X1, void, X3, X4>>));
+    }
+
+    {
+        using L2 = std::pair<X1, X2>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_second<L2, void>, std::pair<X1, void>>));
+    }
+
+    return boost::report_errors();
+}
diff --git a/test/mp_replace_third.cpp b/test/mp_replace_third.cpp
new file mode 100644
index 0000000..5532977
--- /dev/null
+++ b/test/mp_replace_third.cpp
@@ -0,0 +1,48 @@
+
+//  Copyright 2015, 2017 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/algorithm.hpp>
+#include <boost/mp11/list.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+#include <type_traits>
+#include <tuple>
+#include <utility>
+
+struct X1 {};
+struct X2 {};
+struct X3 {};
+struct X4 {};
+
+int main()
+{
+    using boost::mp11::mp_list;
+    using boost::mp11::mp_replace_third;
+
+    {
+        using L3 = mp_list<X1, X2, X3>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_third<L3, void>, mp_list<X1, X2, void>>));
+
+        using L4 = mp_list<X1, X2, X3, X4>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_third<L4, void>, mp_list<X1, X2, void, X4>>));
+    }
+
+    {
+        using L3 = std::tuple<X1, X2, X3>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_third<L3, void>, std::tuple<X1, X2, void>>));
+
+        using L4 = std::tuple<X1, X2, X3, X4>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_third<L4, void>, std::tuple<X1, X2, void, X4>>));
+    }
+
+    return boost::report_errors();
+}