From 4094f2f73f0cdcad97d58545da0511eef2046f65 Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@pdimov.com>
Date: Mon, 22 Jun 2015 03:37:15 +0300
Subject: [PATCH] Add mp_iota, mp_at, mp_take.

---
 include/boost/integer_sequence.hpp        |  2 +
 include/boost/mp11/algorithm.hpp          | 62 ++++++++++++++++-
 include/boost/mp11/detail/mp_map_find.hpp | 40 +++++++++++
 test/Jamfile.v2                           |  5 +-
 test/mp_at.cpp                            | 74 ++++++++++++++++++++
 test/mp_iota.cpp                          | 42 +++++++++++
 test/mp_take.cpp                          | 85 +++++++++++++++++++++++
 7 files changed, 308 insertions(+), 2 deletions(-)
 create mode 100644 include/boost/mp11/detail/mp_map_find.hpp
 create mode 100644 test/mp_at.cpp
 create mode 100644 test/mp_iota.cpp
 create mode 100644 test/mp_take.cpp

diff --git a/include/boost/integer_sequence.hpp b/include/boost/integer_sequence.hpp
index 3fc5175..9ddfc99 100644
--- a/include/boost/integer_sequence.hpp
+++ b/include/boost/integer_sequence.hpp
@@ -49,6 +49,8 @@ template<class T, T N> struct make_integer_sequence_impl_
 {
 private:
 
+    static_assert( N >= 0, "make_integer_sequence<T, N>: N must not be negative" );
+
     static T const M = N / 2;
     static T const R = N % 2;
 
diff --git a/include/boost/mp11/algorithm.hpp b/include/boost/mp11/algorithm.hpp
index d28088c..80a09c0 100644
--- a/include/boost/mp11/algorithm.hpp
+++ b/include/boost/mp11/algorithm.hpp
@@ -12,6 +12,8 @@
 #include <boost/mp11/integral.hpp>
 #include <boost/mp11/utility.hpp>
 #include <boost/mp11/detail/mp_plus.hpp>
+#include <boost/mp11/detail/mp_map_find.hpp>
+#include <boost/integer_sequence.hpp>
 #include <boost/config.hpp>
 #include <boost/detail/workaround.hpp>
 #include <type_traits>
@@ -247,8 +249,66 @@ template<class L, std::size_t N> using mp_drop_c = typename detail::mp_drop_impl
 
 template<class L, class N> using mp_drop = typename detail::mp_drop_impl<L, mp_repeat<mp_list<void>, N>>::type;
 
-// mp_take(_c)<L, N>
+// mp_iota(_c)<N>
+namespace detail
+{
+
+template<class S> struct mp_from_sequence_impl;
+
+template<template<class T, T... I> class S, class U, U... J> struct mp_from_sequence_impl<S<U, J...>>
+{
+    using type = mp_list<std::integral_constant<U, J>...>;
+};
+
+template<class S> using mp_from_sequence = typename mp_from_sequence_impl<S>::type;
+
+} // namespace detail
+
+template<std::size_t N> using mp_iota_c = detail::mp_from_sequence<make_index_sequence<N>>;
+template<class N> using mp_iota = detail::mp_from_sequence<make_integer_sequence<typename std::remove_const<decltype(N::value)>::type, N::value>>;
+
 // mp_at(_c)<L, I>
+namespace detail
+{
+
+template<class L, class I> struct mp_at_impl
+{
+    static_assert( I::value >= 0, "mp_at<L, I>: I must not be negative" );
+
+    using _map = mp_transform<mp_list, mp_iota<mp_size<L>>, L>;
+
+    using type = mp_second<mp_map_find<_map, mp_size_t<I::value>>>;
+};
+
+} // namespace detail
+
+template<class L, std::size_t I> using mp_at_c = typename detail::mp_at_impl<L, mp_size_t<I>>::type;
+
+template<class L, class I> using mp_at = typename detail::mp_at_impl<L, I>::type;
+
+// mp_take(_c)<L, N>
+namespace detail
+{
+
+template<class L, class N> struct mp_take_impl
+{
+    static_assert( N::value >= 0, "mp_take<L, N>: N must not be negative" );
+
+    using _map = mp_transform<mp_list, mp_iota<mp_size<L>>, L>;
+
+    template<class I> using _f = mp_second<mp_map_find<_map, I>>;
+
+    using _ind = mp_iota_c<N::value>;
+
+    using type = mp_assign<L, mp_transform<_f, _ind>>;
+};
+
+} // namespace detail
+
+template<class L, std::size_t N> using mp_take_c = typename detail::mp_take_impl<L, mp_size_t<N>>::type;
+
+template<class L, class N> using mp_take = typename detail::mp_take_impl<L, N>::type;
+
 // mp_find<L, V>
 // mp_find_if<L, P>
 // mp_find_index<L, V>
diff --git a/include/boost/mp11/detail/mp_map_find.hpp b/include/boost/mp11/detail/mp_map_find.hpp
new file mode 100644
index 0000000..6c01e45
--- /dev/null
+++ b/include/boost/mp11/detail/mp_map_find.hpp
@@ -0,0 +1,40 @@
+#ifndef BOOST_MP11_DETAIL_MP_MAP_FIND_HPP_INCLUDED
+#define BOOST_MP11_DETAIL_MP_MAP_FIND_HPP_INCLUDED
+
+//  Copyright 2015 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/utility.hpp>
+
+namespace boost
+{
+
+// mp_map_find
+namespace detail
+{
+
+template<class M, class K> struct mp_map_find_impl;
+
+template<template<class...> class M, class... T, class K> struct mp_map_find_impl<M<T...>, K>
+{
+    using U = mp_inherit<mp_identity<T>...>;
+
+    template<template<class...> class L, class... U> static mp_identity<L<K, U...>> f( mp_identity<L<K, U...>>* );
+    static mp_identity<void> f( ... );
+
+    using V = decltype( f((U*)0) );
+
+    using type = typename V::type;
+};
+
+} // namespace detail
+
+template<class M, class K> using mp_map_find = typename detail::mp_map_find_impl<M, K>::type;
+
+} // namespace boost
+
+#endif // #ifndef BOOST_MP11_DETAIL_MP_MAP_FIND_HPP_INCLUDED
diff --git a/test/Jamfile.v2 b/test/Jamfile.v2
index 41f4d74..e351fc4 100644
--- a/test/Jamfile.v2
+++ b/test/Jamfile.v2
@@ -9,7 +9,7 @@
 import testing ;
 import ../../config/checks/config : requires ;
 
-REQ = ; #[ requires cxx11_variadic_templates cxx11_template_aliases cxx11_hdr_type_traits cxx11_hdr_tuple ] ;
+REQ = ; #[ requires cxx11_variadic_templates cxx11_template_aliases cxx11_decltype cxx11_hdr_type_traits cxx11_hdr_tuple ] ;
 
 # include-only
 compile mp11.cpp : : : $(REQ) ;
@@ -35,6 +35,9 @@ run mp_contains.cpp : : : $(REQ) ;
 run mp_repeat.cpp : : : $(REQ) ;
 run mp_product.cpp : : : $(REQ) ;
 run mp_drop.cpp : : : $(REQ) ;
+run mp_iota.cpp : : : $(REQ) ;
+run mp_at.cpp : : : $(REQ) ;
+run mp_take.cpp : : : $(REQ) ;
 
 # integral
 run integral.cpp : : : $(REQ) ;
diff --git a/test/mp_at.cpp b/test/mp_at.cpp
new file mode 100644
index 0000000..ef22280
--- /dev/null
+++ b/test/mp_at.cpp
@@ -0,0 +1,74 @@
+
+//  Copyright 2015 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::mp_list;
+    using boost::mp_at;
+    using boost::mp_at_c;
+    using boost::mp_size_t;
+
+    {
+        using L1 = mp_list<X1, X2, X3, X4, X5>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_at_c<L1, 0>, X1>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_at_c<L1, 1>, X2>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_at_c<L1, 2>, X3>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_at_c<L1, 3>, X4>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_at_c<L1, 4>, X5>));
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_at<L1, mp_size_t<0>>, X1>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_at<L1, mp_size_t<1>>, X2>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_at<L1, mp_size_t<2>>, X3>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_at<L1, mp_size_t<3>>, X4>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_at<L1, mp_size_t<4>>, X5>));
+    }
+
+    {
+        using L1 = std::tuple<X1, X2, X3, X4, X5>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_at_c<L1, 0>, X1>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_at_c<L1, 1>, X2>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_at_c<L1, 2>, X3>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_at_c<L1, 3>, X4>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_at_c<L1, 4>, X5>));
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_at<L1, mp_size_t<0>>, X1>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_at<L1, mp_size_t<1>>, X2>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_at<L1, mp_size_t<2>>, X3>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_at<L1, mp_size_t<3>>, X4>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_at<L1, mp_size_t<4>>, X5>));
+    }
+
+    {
+        using L1 = std::pair<X1, X2>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_at_c<L1, 0>, X1>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_at_c<L1, 1>, X2>));
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_at<L1, mp_size_t<0>>, X1>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_at<L1, mp_size_t<1>>, X2>));
+    }
+
+    return boost::report_errors();
+}
diff --git a/test/mp_iota.cpp b/test/mp_iota.cpp
new file mode 100644
index 0000000..a1eadfc
--- /dev/null
+++ b/test/mp_iota.cpp
@@ -0,0 +1,42 @@
+
+//  Copyright 2015 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/integral.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+#include <type_traits>
+
+int main()
+{
+    using boost::mp_list;
+    using boost::mp_iota;
+    using boost::mp_iota_c;
+    using boost::mp_int;
+    using boost::mp_size_t;
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_iota_c<0>, mp_list<>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_iota_c<1>, mp_list<mp_size_t<0>>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_iota_c<2>, mp_list<mp_size_t<0>, mp_size_t<1>>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_iota_c<3>, mp_list<mp_size_t<0>, mp_size_t<1>, mp_size_t<2>>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_iota_c<4>, mp_list<mp_size_t<0>, mp_size_t<1>, mp_size_t<2>, mp_size_t<3>>>));
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_iota<mp_size_t<0>>, mp_list<>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_iota<mp_size_t<1>>, mp_list<mp_size_t<0>>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_iota<mp_size_t<2>>, mp_list<mp_size_t<0>, mp_size_t<1>>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_iota<mp_size_t<3>>, mp_list<mp_size_t<0>, mp_size_t<1>, mp_size_t<2>>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_iota<mp_size_t<4>>, mp_list<mp_size_t<0>, mp_size_t<1>, mp_size_t<2>, mp_size_t<3>>>));
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_iota<mp_int<0>>, mp_list<>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_iota<mp_int<1>>, mp_list<mp_int<0>>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_iota<mp_int<2>>, mp_list<mp_int<0>, mp_int<1>>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_iota<mp_int<3>>, mp_list<mp_int<0>, mp_int<1>, mp_int<2>>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_iota<mp_int<4>>, mp_list<mp_int<0>, mp_int<1>, mp_int<2>, mp_int<3>>>));
+
+    return boost::report_errors();
+}
diff --git a/test/mp_take.cpp b/test/mp_take.cpp
new file mode 100644
index 0000000..eac3f12
--- /dev/null
+++ b/test/mp_take.cpp
@@ -0,0 +1,85 @@
+
+//  Copyright 2015 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::mp_list;
+    using boost::mp_take;
+    using boost::mp_take_c;
+    using boost::mp_size_t;
+
+    {
+        using L1 = mp_list<>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take_c<L1, 0>, L1>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take<L1, mp_size_t<0>>, L1>));
+
+        using L2 = mp_list<X1, X2, X3, X4, X5>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take_c<L2, 0>, mp_list<>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take_c<L2, 1>, mp_list<X1>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take_c<L2, 2>, mp_list<X1, X2>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take_c<L2, 3>, mp_list<X1, X2, X3>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take_c<L2, 4>, mp_list<X1, X2, X3, X4>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take_c<L2, 5>, mp_list<X1, X2, X3, X4, X5>>));
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take<L2, mp_size_t<0>>, mp_list<>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take<L2, mp_size_t<1>>, mp_list<X1>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take<L2, mp_size_t<2>>, mp_list<X1, X2>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take<L2, mp_size_t<3>>, mp_list<X1, X2, X3>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take<L2, mp_size_t<4>>, mp_list<X1, X2, X3, X4>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take<L2, mp_size_t<5>>, mp_list<X1, X2, X3, X4, X5>>));
+    }
+
+    {
+        using L1 = std::tuple<>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take_c<L1, 0>, L1>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take<L1, mp_size_t<0>>, L1>));
+
+        using L2 = std::tuple<X1, X2, X3, X4, X5>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take_c<L2, 0>, std::tuple<>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take_c<L2, 1>, std::tuple<X1>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take_c<L2, 2>, std::tuple<X1, X2>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take_c<L2, 3>, std::tuple<X1, X2, X3>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take_c<L2, 4>, std::tuple<X1, X2, X3, X4>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take_c<L2, 5>, std::tuple<X1, X2, X3, X4, X5>>));
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take<L2, mp_size_t<0>>, std::tuple<>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take<L2, mp_size_t<1>>, std::tuple<X1>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take<L2, mp_size_t<2>>, std::tuple<X1, X2>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take<L2, mp_size_t<3>>, std::tuple<X1, X2, X3>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take<L2, mp_size_t<4>>, std::tuple<X1, X2, X3, X4>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take<L2, mp_size_t<5>>, std::tuple<X1, X2, X3, X4, X5>>));
+    }
+
+    {
+        using L1 = std::pair<X1, X2>;
+
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take_c<L1, 2>, L1>));
+        BOOST_TEST_TRAIT_TRUE((std::is_same<mp_take<L1, mp_size_t<2>>, L1>));
+    }
+
+    return boost::report_errors();
+}