From d3f4b099d222fe0b3ee1ab279881bcd1fe82da98 Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@pdimov.com>
Date: Fri, 24 Mar 2017 18:10:07 +0200
Subject: [PATCH] Unroll mp_reverse_fold.

---
 include/boost/mp11/algorithm.hpp |  6 ++++++
 test/mp_reverse_fold.cpp         | 23 ++++++++++++++++++++++-
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/include/boost/mp11/algorithm.hpp b/include/boost/mp11/algorithm.hpp
index 8a83e36..d71b77c 100644
--- a/include/boost/mp11/algorithm.hpp
+++ b/include/boost/mp11/algorithm.hpp
@@ -796,6 +796,12 @@ template<template<class...> class L, class T1, class... T, class V, template<cla
     using type = F<T1, rest>;
 };
 
+template<template<class...> class L, class T1, class T2, class T3, class T4, class T5, class T6, class T7, class T8, class T9, class T10, class... T, class V, template<class...> class F> struct mp_reverse_fold_impl<L<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T...>, V, F>
+{
+    using rest = typename mp_reverse_fold_impl<L<T...>, V, F>::type;
+    using type = F<T1, F<T2, F<T3, F<T4, F<T5, F<T6, F<T7, F<T8, F<T9, F<T10, rest>>>>>>>>>>;
+};
+
 } // namespace detail
 
 template<class L, class V, template<class...> class F> using mp_reverse_fold = typename detail::mp_reverse_fold_impl<L, V, F>::type;
diff --git a/test/mp_reverse_fold.cpp b/test/mp_reverse_fold.cpp
index f88b645..0556bee 100644
--- a/test/mp_reverse_fold.cpp
+++ b/test/mp_reverse_fold.cpp
@@ -1,5 +1,5 @@
 
-//  Copyright 2015 Peter Dimov.
+// Copyright 2015-2017 Peter Dimov.
 //
 // Distributed under the Boost Software License, Version 1.0.
 //
@@ -9,6 +9,7 @@
 
 #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>
@@ -55,5 +56,25 @@ int main()
         BOOST_TEST_TRAIT_TRUE((std::is_same<mp_reverse_fold<std::tuple<X1, X2, X3, X4>, mp_list<>, rev_push_front>, mp_list<X1, X2, X3, X4>>));
     }
 
+    using boost::mp11::mp_iota_c;
+    using boost::mp11::mp_reverse;
+    using boost::mp11::mp_size_t;
+    using boost::mp11::mp_plus;
+
+    {
+        int const N = 37;
+
+        using L = mp_iota_c<N>;
+
+        using R1 = mp_reverse_fold<L, mp_list<>, rev_push_front>;
+        BOOST_TEST_TRAIT_TRUE((std::is_same<R1, L>));
+
+        using R2 = mp_reverse_fold<L, mp_list<>, rev_push_back>;
+        BOOST_TEST_TRAIT_TRUE((std::is_same<R2, mp_reverse<L>>));
+
+        using R3 = mp_reverse_fold<L, mp_size_t<0>, mp_plus>;
+        BOOST_TEST_TRAIT_TRUE((std::is_same<R3, mp_size_t<N*(N-1)/2>>));
+    }
+
     return boost::report_errors();
 }