From 7e8d618793eecf3a389edc352230147abdadd093 Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@pdimov.com>
Date: Sat, 18 Mar 2017 20:20:31 +0200
Subject: [PATCH] Add mp_replace_at(_c)

---
 include/boost/mp11/algorithm.hpp | 19 ++++++++++
 test/Jamfile.v2                  |  2 ++
 test/mp_replace_at.cpp           | 60 ++++++++++++++++++++++++++++++++
 test/mp_replace_at_c.cpp         | 56 +++++++++++++++++++++++++++++
 4 files changed, 137 insertions(+)
 create mode 100644 test/mp_replace_at.cpp
 create mode 100644 test/mp_replace_at_c.cpp

diff --git a/include/boost/mp11/algorithm.hpp b/include/boost/mp11/algorithm.hpp
index 144f1f9..4a6cafe 100644
--- a/include/boost/mp11/algorithm.hpp
+++ b/include/boost/mp11/algorithm.hpp
@@ -834,6 +834,25 @@ template<class L, template<class...> class P> using mp_none_of = mp_bool< mp_cou
 // mp_any_of<L, P>
 template<class L, template<class...> class P> using mp_any_of = mp_bool< mp_count_if<L, P>::value != 0 >;
 
+// mp_replace_at_c<L, I, W>
+namespace detail
+{
+
+template<class L, class I, class W> struct mp_replace_at_impl
+{
+    static_assert( I::value >= 0, "mp_replace_at<L, I, W>: I must not be negative" );
+
+    template<class T1, class T2> using _p = std::is_same<T2, mp_size_t<I::value>>;
+    template<class T1, class T2> using _f = W;
+
+    using type = mp_transform_if<_p, _f, L, mp_iota<mp_size<L>>>;
+};
+
+} // namespace detail
+
+template<class L, class I, class W> using mp_replace_at = typename detail::mp_replace_at_impl<L, I, W>::type;
+template<class L, std::size_t I, class W> using mp_replace_at_c = typename detail::mp_replace_at_impl<L, mp_size_t<I>, W>::type;
+
 } // namespace mp11
 } // namespace boost
 
diff --git a/test/Jamfile.v2 b/test/Jamfile.v2
index 14d21b0..8819294 100644
--- a/test/Jamfile.v2
+++ b/test/Jamfile.v2
@@ -60,6 +60,8 @@ run mp_unique.cpp : : : $(REQ) ;
 run mp_all_of.cpp : : : $(REQ) ;
 run mp_any_of.cpp : : : $(REQ) ;
 run mp_none_of.cpp : : : $(REQ) ;
+run mp_replace_at.cpp : : : $(REQ) ;
+run mp_replace_at_c.cpp : : : $(REQ) ;
 
 # integral
 run integral.cpp : : : $(REQ) ;
diff --git a/test/mp_replace_at.cpp b/test/mp_replace_at.cpp
new file mode 100644
index 0000000..faf2289
--- /dev/null
+++ b/test/mp_replace_at.cpp
@@ -0,0 +1,60 @@
+
+//  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/mp11/integral.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+#include <type_traits>
+#include <tuple>
+#include <utility>
+
+struct X1 {};
+struct X2 {};
+struct X3 {};
+struct X4 {};
+struct X5 {};
+
+int main()
+{
+    using boost::mp11::mp_list;
+    using boost::mp11::mp_replace_at;
+    using boost::mp11::mp_int;
+    using boost::mp11::mp_true;
+    using boost::mp11::mp_false;
+
+    {
+        using L = mp_list<X1, X2, X3, X4, X5>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_at<L, mp_int<0>, void>, mp_list<void, X2, X3, X4, X5>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_at<L, mp_int<1>, void>, mp_list<X1, void, X3, X4, X5>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_at<L, mp_int<2>, void>, mp_list<X1, X2, void, X4, X5>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_at<L, mp_int<3>, void>, mp_list<X1, X2, X3, void, X5>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_at<L, mp_int<4>, void>, mp_list<X1, X2, X3, X4, void>>));
+    }
+
+    {
+        using L = std::tuple<X1, X2, X3, X4, X5>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_at<L, mp_int<0>, void>, std::tuple<void, X2, X3, X4, X5>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_at<L, mp_int<1>, void>, std::tuple<X1, void, X3, X4, X5>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_at<L, mp_int<2>, void>, std::tuple<X1, X2, void, X4, X5>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_at<L, mp_int<3>, void>, std::tuple<X1, X2, X3, void, X5>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_at<L, mp_int<4>, void>, std::tuple<X1, X2, X3, X4, void>>));
+    }
+
+    {
+        using L = std::pair<X1, X2>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_at<L, mp_false, void>, std::pair<void, X2>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_at<L, mp_true, void>, std::pair<X1, void>>));
+    }
+
+    return boost::report_errors();
+}
diff --git a/test/mp_replace_at_c.cpp b/test/mp_replace_at_c.cpp
new file mode 100644
index 0000000..5a5bd54
--- /dev/null
+++ b/test/mp_replace_at_c.cpp
@@ -0,0 +1,56 @@
+
+//  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 {};
+struct X5 {};
+
+int main()
+{
+    using boost::mp11::mp_list;
+    using boost::mp11::mp_replace_at_c;
+
+    {
+        using L = mp_list<X1, X2, X3, X4, X5>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_at_c<L, 0, void>, mp_list<void, X2, X3, X4, X5>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_at_c<L, 1, void>, mp_list<X1, void, X3, X4, X5>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_at_c<L, 2, void>, mp_list<X1, X2, void, X4, X5>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_at_c<L, 3, void>, mp_list<X1, X2, X3, void, X5>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_at_c<L, 4, void>, mp_list<X1, X2, X3, X4, void>>));
+    }
+
+    {
+        using L = std::tuple<X1, X2, X3, X4, X5>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_at_c<L, 0, void>, std::tuple<void, X2, X3, X4, X5>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_at_c<L, 1, void>, std::tuple<X1, void, X3, X4, X5>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_at_c<L, 2, void>, std::tuple<X1, X2, void, X4, X5>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_at_c<L, 3, void>, std::tuple<X1, X2, X3, void, X5>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_at_c<L, 4, void>, std::tuple<X1, X2, X3, X4, void>>));
+    }
+
+    {
+        using L = std::pair<X1, X2>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_at_c<L, 0, void>, std::pair<void, X2>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_replace_at_c<L, 1, void>, std::pair<X1, void>>));
+    }
+
+    return boost::report_errors();
+}