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- // Copyright Louis Dionne 2013-2017
- // Distributed under the Boost Software License, Version 1.0.
- // (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
- // Make sure `assert` always triggers an assertion
- #ifdef NDEBUG
- # undef NDEBUG
- #endif
- //! [additional_setup]
- #include <cassert>
- #include <iostream>
- #include <string>
- struct Fish { std::string name; };
- struct Cat { std::string name; };
- struct Dog { std::string name; };
- //! [additional_setup]
- //! [includes]
- #include <boost/hana.hpp>
- namespace hana = boost::hana;
- //! [includes]
- int main() {
- //! [animals]
- auto animals = hana::make_tuple(Fish{"Nemo"}, Cat{"Garfield"}, Dog{"Snoopy"});
- //! [animals]
- //! [algorithms]
- using namespace hana::literals;
- // Access tuple elements with operator[] instead of std::get.
- Cat garfield = animals[1_c];
- // Perform high level algorithms on tuples (this is like std::transform)
- auto names = hana::transform(animals, [](auto a) {
- return a.name;
- });
- assert(hana::reverse(names) == hana::make_tuple("Snoopy", "Garfield", "Nemo"));
- //! [algorithms]
- //! [type-level]
- auto animal_types = hana::make_tuple(hana::type_c<Fish*>, hana::type_c<Cat&>, hana::type_c<Dog>);
- auto no_pointers = hana::remove_if(animal_types, [](auto a) {
- return hana::traits::is_pointer(a);
- });
- static_assert(no_pointers == hana::make_tuple(hana::type_c<Cat&>, hana::type_c<Dog>), "");
- //! [type-level]
- //! [has_name]
- auto has_name = hana::is_valid([](auto&& x) -> decltype((void)x.name) { });
- static_assert(has_name(garfield), "");
- static_assert(!has_name(1), "");
- //! [has_name]
- #if 0
- //! [screw_up]
- auto serialize = [](std::ostream& os, auto const& object) {
- hana::for_each(os, [&](auto member) {
- // ^^ oopsie daisy!
- os << member << std::endl;
- });
- };
- //! [screw_up]
- #endif
- //! [serialization]
- // 1. Give introspection capabilities to 'Person'
- struct Person {
- BOOST_HANA_DEFINE_STRUCT(Person,
- (std::string, name),
- (int, age)
- );
- };
- // 2. Write a generic serializer (bear with std::ostream for the example)
- auto serialize = [](std::ostream& os, auto const& object) {
- hana::for_each(hana::members(object), [&](auto member) {
- os << member << std::endl;
- });
- };
- // 3. Use it
- Person john{"John", 30};
- serialize(std::cout, john);
- // output:
- // John
- // 30
- //! [serialization]
- }
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