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b32b8144 | 1 | // Copyright Louis Dionne 2013-2017 |
7c673cae FG |
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 | } |