102 lines
2.3 KiB
C++
102 lines
2.3 KiB
C++
// 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]
|
|
|
|
}
|