1 // Copyright Louis Dionne 2013-2017
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 // Make sure `assert` always triggers an assertion
6 #ifdef NDEBUG
7 # undef NDEBUG
8 #endif
9
10 //! [additional_setup]
11 #include <cassert>
12 #include <iostream>
13 #include <string>
14
15 struct Fish { std::string name; };
16 struct Cat { std::string name; };
17 struct Dog { std::string name; };
18 //! [additional_setup]
19
20 //! [includes]
21 #include <boost/hana.hpp>
22 namespace hana = boost::hana;
23 //! [includes]
24
25
main()26 int main() {
27
28 //! [animals]
29 auto animals = hana::make_tuple(Fish{"Nemo"}, Cat{"Garfield"}, Dog{"Snoopy"});
30 //! [animals]
31
32 //! [algorithms]
33 using namespace hana::literals;
34
35 // Access tuple elements with operator[] instead of std::get.
36 Cat garfield = animals[1_c];
37
38 // Perform high level algorithms on tuples (this is like std::transform)
39 auto names = hana::transform(animals, [](auto a) {
40 return a.name;
41 });
42
43 assert(hana::reverse(names) == hana::make_tuple("Snoopy", "Garfield", "Nemo"));
44 //! [algorithms]
45
46
47 //! [type-level]
48 auto animal_types = hana::make_tuple(hana::type_c<Fish*>, hana::type_c<Cat&>, hana::type_c<Dog>);
49
50 auto no_pointers = hana::remove_if(animal_types, [](auto a) {
51 return hana::traits::is_pointer(a);
52 });
53
54 static_assert(no_pointers == hana::make_tuple(hana::type_c<Cat&>, hana::type_c<Dog>), "");
55 //! [type-level]
56
57
58 //! [has_name]
59 auto has_name = hana::is_valid([](auto&& x) -> decltype((void)x.name) { });
60
61 static_assert(has_name(garfield), "");
62 static_assert(!has_name(1), "");
63 //! [has_name]
64
65 #if 0
66 //! [screw_up]
67 auto serialize = [](std::ostream& os, auto const& object) {
68 hana::for_each(os, [&](auto member) {
69 // ^^ oopsie daisy!
70 os << member << std::endl;
71 });
72 };
73 //! [screw_up]
74 #endif
75
76 //! [serialization]
77 // 1. Give introspection capabilities to 'Person'
78 struct Person {
79 BOOST_HANA_DEFINE_STRUCT(Person,
80 (std::string, name),
81 (int, age)
82 );
83 };
84
85 // 2. Write a generic serializer (bear with std::ostream for the example)
86 auto serialize = [](std::ostream& os, auto const& object) {
87 hana::for_each(hana::members(object), [&](auto member) {
88 os << member << std::endl;
89 });
90 };
91
92 // 3. Use it
93 Person john{"John", 30};
94 serialize(std::cout, john);
95
96 // output:
97 // John
98 // 30
99 //! [serialization]
100
101 }
102