1 /*!
2 @file
3 Defines `boost::hana::insert`.
4 
5 @copyright Louis Dionne 2013-2017
6 Distributed under the Boost Software License, Version 1.0.
7 (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
8  */
9 
10 #ifndef BOOST_HANA_INSERT_HPP
11 #define BOOST_HANA_INSERT_HPP
12 
13 #include <boost/hana/fwd/insert.hpp>
14 
15 #include <boost/hana/append.hpp>
16 #include <boost/hana/concat.hpp>
17 #include <boost/hana/concept/sequence.hpp>
18 #include <boost/hana/config.hpp>
19 #include <boost/hana/core/dispatch.hpp>
20 #include <boost/hana/drop_front.hpp>
21 #include <boost/hana/take_front.hpp>
22 
23 
24 BOOST_HANA_NAMESPACE_BEGIN
25     //! @cond
26     template <typename Set, typename ...Args>
operator ()(Set && set,Args &&...args) const27     constexpr decltype(auto) insert_t::operator()(Set&& set, Args&& ...args) const {
28         return insert_impl<typename hana::tag_of<Set>::type>::apply(
29             static_cast<Set&&>(set),
30             static_cast<Args&&>(args)...
31         );
32     }
33     //! @endcond
34 
35     template <typename T, bool condition>
36     struct insert_impl<T, when<condition>> : default_ {
37         template <typename ...Args>
38         static constexpr auto apply(Args&& ...) = delete;
39     };
40 
41     template <typename S>
42     struct insert_impl<S, when<Sequence<S>::value>> {
43         template <typename Xs, typename N, typename Element>
applyinsert_impl44         static constexpr auto apply(Xs&& xs, N const& n, Element&& e) {
45             return hana::concat(hana::append(hana::take_front(xs, n),
46                                              static_cast<Element&&>(e)),
47                                 hana::drop_front(xs, n));
48         }
49     };
50 BOOST_HANA_NAMESPACE_END
51 
52 #endif // !BOOST_HANA_INSERT_HPP
53