56 lines
1.5 KiB
C++
56 lines
1.5 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)
|
|
|
|
#include <boost/hana.hpp>
|
|
#include <boost/hana/ext/std/integral_constant.hpp>
|
|
|
|
#include <memory>
|
|
#include <string>
|
|
#include <type_traits>
|
|
#include <utility>
|
|
namespace hana = boost::hana;
|
|
|
|
|
|
|
|
namespace ns1 {
|
|
//! [make_unique.if_]
|
|
template <typename T, typename ...Args>
|
|
std::unique_ptr<T> make_unique(Args&&... args) {
|
|
return hana::if_(std::is_constructible<T, Args...>{},
|
|
[](auto&& ...x) { return std::unique_ptr<T>(new T(std::forward<Args>(x)...)); },
|
|
[](auto&& ...x) { return std::unique_ptr<T>(new T{std::forward<Args>(x)...}); }
|
|
)(std::forward<Args>(args)...);
|
|
}
|
|
//! [make_unique.if_]
|
|
}
|
|
|
|
|
|
namespace ns2 {
|
|
//! [make_unique.eval_if]
|
|
template <typename T, typename ...Args>
|
|
std::unique_ptr<T> make_unique(Args&&... args) {
|
|
return hana::eval_if(std::is_constructible<T, Args...>{},
|
|
[&](auto _) { return std::unique_ptr<T>(new T(std::forward<Args>(_(args))...)); },
|
|
[&](auto _) { return std::unique_ptr<T>(new T{std::forward<Args>(_(args))...}); }
|
|
);
|
|
}
|
|
//! [make_unique.eval_if]
|
|
}
|
|
|
|
struct Student {
|
|
std::string name;
|
|
int age;
|
|
};
|
|
|
|
int main() {
|
|
{
|
|
std::unique_ptr<int> a = ns1::make_unique<int>(3);
|
|
std::unique_ptr<Student> b = ns1::make_unique<Student>("Bob", 25);
|
|
}
|
|
{
|
|
std::unique_ptr<int> a = ns2::make_unique<int>(3);
|
|
std::unique_ptr<Student> b = ns2::make_unique<Student>("Bob", 25);
|
|
}
|
|
}
|