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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/config.hpp> | |
7 | #include <boost/hana/equal.hpp> | |
8 | #include <boost/hana/eval_if.hpp> | |
9 | #include <boost/hana/lazy.hpp> | |
10 | #include <boost/hana/traits.hpp> | |
11 | #include <boost/hana/type.hpp> | |
12 | namespace hana = boost::hana; | |
13 | ||
14 | ||
15 | // eval_if with heterogeneous branches and a Constant condition | |
16 | BOOST_HANA_CONSTEXPR_LAMBDA auto safe_make_unsigned = [](auto t) { | |
17 | return hana::eval_if(hana::traits::is_integral(t), | |
18 | hana::make_lazy(hana::traits::make_unsigned)(t), | |
19 | hana::make_lazy(t) | |
20 | ); | |
21 | }; | |
22 | ||
23 | BOOST_HANA_CONSTANT_CHECK(safe_make_unsigned(hana::type_c<void>) == hana::type_c<void>); | |
24 | BOOST_HANA_CONSTANT_CHECK(safe_make_unsigned(hana::type_c<int>) == hana::type_c<unsigned int>); | |
25 | ||
26 | ||
27 | // eval_if with homogeneous branches and a constexpr or runtime condition | |
28 | BOOST_HANA_CONSTEXPR_LAMBDA auto safe_divide = [](auto x, auto y) { | |
29 | return hana::eval_if(y == 0, | |
30 | [=](auto) { return 0; }, | |
31 | [=](auto _) { return _(x) / y; } | |
32 | ); | |
33 | }; | |
34 | ||
35 | int main() { | |
36 | BOOST_HANA_CONSTEXPR_CHECK(safe_divide(6, 3) == 2); | |
37 | BOOST_HANA_CONSTEXPR_CHECK(safe_divide(6, 0) == 0); | |
38 | } |