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1 /*!
2 @file
3 Forward declares `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_FWD_INSERT_HPP
11 #define BOOST_HANA_FWD_INSERT_HPP
12
13 #include <boost/hana/config.hpp>
14 #include <boost/hana/core/when.hpp>
15
16
17 BOOST_HANA_NAMESPACE_BEGIN
18 // Note: This function is documented per datatype/concept only.
19 //! @cond
20 template <typename T, typename = void>
21 struct insert_impl : insert_impl<T, when<true>> { };
22 //! @endcond
23
24 struct insert_t {
25 template <typename Set, typename ...Args>
26 constexpr decltype(auto) operator()(Set&& set, Args&& ...args) const;
27 };
28
29 constexpr insert_t insert{};
30
31
32 //! Insert a value at a given index in a sequence.
33 //! @ingroup group-Sequence
34 //!
35 //! Given a sequence, an index and an element to insert, `insert` inserts
36 //! the element at the given index.
37 //!
38 //! @param xs
39 //! The sequence in which a value should be inserted.
40 //!
41 //! @param n
42 //! The index at which an element should be inserted. This must be a
43 //! non-negative `Constant` of an integral type, and it must also be
44 //! true that `n < length(xs)` if `xs` is a finite sequence.
45 //!
46 //! @param element
47 //! The element to insert in the sequence.
48 //!
49 //!
50 //! Example
51 //! -------
52 //! @include example/insert.cpp
53 #ifdef BOOST_HANA_DOXYGEN_INVOKED
54 constexpr auto insert = [](auto&& xs, auto&& n, auto&& element) {
55 return tag-dispatched;
56 };
57 #endif
58 BOOST_HANA_NAMESPACE_END
59
60 #endif // !BOOST_HANA_FWD_INSERT_HPP