]>
Commit | Line | Data |
---|---|---|
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/config.hpp> | |
7 | #include <boost/hana/contains.hpp> | |
8 | #include <boost/hana/equal.hpp> | |
9 | #include <boost/hana/if.hpp> | |
10 | #include <boost/hana/monadic_compose.hpp> | |
11 | #include <boost/hana/optional.hpp> | |
12 | #include <boost/hana/tuple.hpp> | |
13 | #include <boost/hana/type.hpp> | |
14 | namespace hana = boost::hana; | |
15 | ||
16 | ||
17 | int main() { | |
18 | BOOST_HANA_CONSTEXPR_LAMBDA auto block = [](auto ...types) { | |
19 | return [=](auto x) { | |
20 | return hana::if_(hana::contains(hana::make_tuple(types...), hana::typeid_(x)), | |
21 | hana::nothing, | |
22 | hana::just(x) | |
23 | ); | |
24 | }; | |
25 | }; | |
26 | ||
27 | BOOST_HANA_CONSTEXPR_LAMBDA auto f = block(hana::type_c<double>); | |
28 | BOOST_HANA_CONSTEXPR_LAMBDA auto g = block(hana::type_c<int>); | |
29 | BOOST_HANA_CONSTEXPR_LAMBDA auto h = hana::monadic_compose(g, f); | |
30 | BOOST_HANA_CONSTANT_CHECK(h(1) == hana::nothing); // fails inside g; 1 has type int | |
31 | BOOST_HANA_CONSTANT_CHECK(h(1.2) == hana::nothing); // fails inside f; 1.2 has type double | |
32 | BOOST_HANA_CONSTEXPR_CHECK(h('x') == hana::just('x')); // ok; 'x' has type char | |
33 | } |