| 1 | // Copyright Louis Dionne 2013-2022 |
|---|---|
| 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 | #include <boost/hana/assert.hpp> |
| 6 | #include <boost/hana/eval.hpp> |
| 7 | #include <boost/hana/extend.hpp> |
| 8 | #include <boost/hana/extract.hpp> |
| 9 | #include <boost/hana/lazy.hpp> |
| 10 | |
| 11 | #include <sstream> |
| 12 | namespace hana = boost::hana; |
| 13 | |
| 14 | |
| 15 | int main() { |
| 16 | std::stringstream s("1 2 3"); |
| 17 | auto i = hana::make_lazy([&] { |
| 18 | int i; |
| 19 | s >> i; |
| 20 | return i; |
| 21 | })(); |
| 22 | |
| 23 | auto i_plus_one = hana::extend(i, [](auto lazy_int) { |
| 24 | return hana::eval(lazy_int) + 1; |
| 25 | }); |
| 26 | |
| 27 | BOOST_HANA_RUNTIME_CHECK(hana::extract(i_plus_one) == 2); |
| 28 | BOOST_HANA_RUNTIME_CHECK(hana::extract(i_plus_one) == 3); |
| 29 | BOOST_HANA_RUNTIME_CHECK(hana::extract(i_plus_one) == 4); |
| 30 | } |
| 31 |