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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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