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b32b8144 | 1 | // Copyright Louis Dionne 2013-2017 |
7c673cae FG |
2 | // Distributed under the Boost Software License, Version 1.0. |
3 | // (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt) | |
4 | ||
5 | #include <boost/hana/at.hpp> | |
6 | #include <boost/hana/back.hpp> | |
7 | #include <boost/hana/core/to.hpp> | |
8 | #include <boost/hana/front.hpp> | |
9 | #include <boost/hana/functional/on.hpp> | |
10 | #include <boost/hana/integral_constant.hpp> | |
11 | #include <boost/hana/length.hpp> | |
12 | #include <boost/hana/less.hpp> | |
13 | #include <boost/hana/pair.hpp> | |
14 | #include <boost/hana/range.hpp> | |
15 | #include <boost/hana/sort.hpp> | |
16 | #include <boost/hana/transform.hpp> | |
17 | #include <boost/hana/tuple.hpp> | |
18 | #include <boost/hana/type.hpp> | |
19 | #include <boost/hana/zip.hpp> | |
20 | ||
21 | #include <type_traits> | |
22 | namespace hana = boost::hana; | |
23 | using namespace hana::literals; | |
24 | ||
25 | ||
26 | auto indexed_sort = [](auto list, auto predicate) { | |
27 | auto indexed_list = hana::zip( | |
28 | list, | |
29 | hana::to_tuple(hana::make_range(0_c, hana::length(list))) | |
30 | ); | |
31 | auto sorted = hana::sort.by(predicate ^hana::on^ hana::front, indexed_list); | |
32 | return hana::make_pair(hana::transform(sorted, hana::front), | |
33 | hana::transform(sorted, hana::back)); | |
34 | }; | |
35 | ||
36 | int main() { | |
37 | auto types = hana::tuple_t<char[4], char[2], char[1], char[5], char[3]>; | |
38 | auto sorted = indexed_sort(types, [](auto t, auto u) { | |
39 | return hana::sizeof_(t) < hana::sizeof_(u); | |
40 | }); | |
41 | using Tup = decltype( | |
42 | hana::unpack(hana::first(sorted), hana::template_<hana::tuple>) | |
43 | )::type; | |
44 | auto indices = hana::second(indexed_sort(hana::second(sorted), hana::less)); | |
45 | ||
46 | // When accessed through the indices sequence, the tuple appears to be | |
47 | // ordered as the `types` above. However, as can be seen in the | |
48 | // static_assert below, the tuple is actually ordered differently. | |
49 | Tup tup; | |
50 | char const(&a)[4] = tup[indices[0_c]]; | |
51 | char const(&b)[2] = tup[indices[1_c]]; | |
52 | char const(&c)[1] = tup[indices[2_c]]; | |
53 | char const(&d)[5] = tup[indices[3_c]]; | |
54 | char const(&e)[3] = tup[indices[4_c]]; | |
55 | ||
56 | static_assert(std::is_same< | |
57 | Tup, | |
58 | hana::tuple<char[1], char[2], char[3], char[4], char[5]> | |
59 | >{}, ""); | |
60 | ||
61 | (void)a; (void)b; (void)c; (void)d; (void)e; | |
62 | } |