From ea688030928b7232a41653bd573c944f503fb312 Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@pdimov.com>
Date: Sun, 15 Oct 2017 14:33:50 +0300
Subject: [PATCH] Move mp_fold to detail/mp_fold.hpp

---
 include/boost/mp11/algorithm.hpp      | 46 +------------------
 include/boost/mp11/detail/mp_fold.hpp | 65 +++++++++++++++++++++++++++
 2 files changed, 67 insertions(+), 44 deletions(-)
 create mode 100644 include/boost/mp11/detail/mp_fold.hpp

diff --git a/include/boost/mp11/algorithm.hpp b/include/boost/mp11/algorithm.hpp
index 6a89bc8..4e5bf03 100644
--- a/include/boost/mp11/algorithm.hpp
+++ b/include/boost/mp11/algorithm.hpp
@@ -17,6 +17,7 @@
 #include <boost/mp11/detail/mp_plus.hpp>
 #include <boost/mp11/detail/mp_map_find.hpp>
 #include <boost/mp11/detail/mp_with_index.hpp>
+#include <boost/mp11/detail/mp_fold.hpp>
 #include <boost/mp11/detail/config.hpp>
 #include <boost/mp11/integer_sequence.hpp>
 #include <boost/config.hpp>
@@ -29,17 +30,6 @@ namespace boost
 namespace mp11
 {
 
-// mp_fold<L, V, F> forward declaration
-namespace detail
-{
-
-template<class L, class V, template<class...> class F> struct mp_fold_impl;
-
-} // namespace detail
-
-template<class L, class V, template<class...> class F> using mp_fold = typename detail::mp_fold_impl<L, V, F>::type;
-template<class L, class V, class Q> using mp_fold_q = mp_fold<L, V, Q::template fn>;
-
 // mp_transform<F, L...>
 namespace detail
 {
@@ -767,39 +757,7 @@ template<template<class...> class L, class T1, class T2, class T3, class T4, cla
 template<class L> using mp_reverse = typename detail::mp_reverse_impl<L>::type;
 
 // mp_fold<L, V, F>
-namespace detail
-{
-
-template<class L, class V, template<class...> class F> struct mp_fold_impl;
-
-#if defined( BOOST_MSVC ) && BOOST_WORKAROUND( BOOST_MSVC, <= 1800 )
-
-template<template<class...> class L, class... T, class V, template<class...> class F> struct mp_fold_impl<L<T...>, V, F>
-{
-    static_assert( sizeof...(T) == 0, "T... must be empty" );
-    using type = V;
-};
-
-#else
-
-template<template<class...> class L, class V, template<class...> class F> struct mp_fold_impl<L<>, V, F>
-{
-    using type = V;
-};
-
-#endif
-
-template<template<class...> class L, class T1, class... T, class V, template<class...> class F> struct mp_fold_impl<L<T1, T...>, V, F>
-{
-    using type = typename mp_fold_impl<L<T...>, F<V, T1>, F>::type;
-};
-
-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_fold_impl<L<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T...>, V, F>
-{
-    using type = typename mp_fold_impl<L<T...>, F<F<F<F<F<F<F<F<F<F<V, T1>, T2>, T3>, T4>, T5>, T6>, T7>, T8>, T9>, T10>, F>::type;
-};
-
-} // namespace detail
+//   in detail/mp_fold.hpp
 
 // mp_reverse_fold<L, V, F>
 namespace detail
diff --git a/include/boost/mp11/detail/mp_fold.hpp b/include/boost/mp11/detail/mp_fold.hpp
new file mode 100644
index 0000000..62bc785
--- /dev/null
+++ b/include/boost/mp11/detail/mp_fold.hpp
@@ -0,0 +1,65 @@
+#ifndef BOOST_MP11_DETAIL_MP_FOLD_HPP_INCLUDED
+#define BOOST_MP11_DETAIL_MP_FOLD_HPP_INCLUDED
+
+//  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/integral.hpp>
+#include <boost/mp11/detail/mp_plus.hpp>
+#include <boost/mp11/detail/config.hpp>
+#include <boost/config.hpp>
+
+namespace boost
+{
+namespace mp11
+{
+
+// mp_fold<L, V, F>
+namespace detail
+{
+
+template<class L, class V, template<class...> class F> struct mp_fold_impl
+{
+// An error "no type named 'type'" here means that the first argument to mp_fold is not a list
+};
+
+#if defined( BOOST_MSVC ) && BOOST_WORKAROUND( BOOST_MSVC, <= 1800 )
+
+template<template<class...> class L, class... T, class V, template<class...> class F> struct mp_fold_impl<L<T...>, V, F>
+{
+    static_assert( sizeof...(T) == 0, "T... must be empty" );
+    using type = V;
+};
+
+#else
+
+template<template<class...> class L, class V, template<class...> class F> struct mp_fold_impl<L<>, V, F>
+{
+    using type = V;
+};
+
+#endif
+
+template<template<class...> class L, class T1, class... T, class V, template<class...> class F> struct mp_fold_impl<L<T1, T...>, V, F>
+{
+    using type = typename mp_fold_impl<L<T...>, F<V, T1>, F>::type;
+};
+
+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_fold_impl<L<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T...>, V, F>
+{
+    using type = typename mp_fold_impl<L<T...>, F<F<F<F<F<F<F<F<F<F<V, T1>, T2>, T3>, T4>, T5>, T6>, T7>, T8>, T9>, T10>, F>::type;
+};
+
+} // namespace detail
+
+template<class L, class V, template<class...> class F> using mp_fold = typename detail::mp_fold_impl<L, V, F>::type;
+template<class L, class V, class Q> using mp_fold_q = mp_fold<L, V, Q::template fn>;
+
+} // namespace mp11
+} // namespace boost
+
+#endif // #ifndef BOOST_MP11_DETAIL_MP_FOLD_HPP_INCLUDED