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- // 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/assert.hpp>
- #include <boost/hana/config.hpp>
- #include <boost/hana/equal.hpp>
- #include <boost/hana/eval_if.hpp>
- #include <boost/hana/lazy.hpp>
- #include <boost/hana/traits.hpp>
- #include <boost/hana/type.hpp>
- namespace hana = boost::hana;
- // eval_if with heterogeneous branches and a Constant condition
- BOOST_HANA_CONSTEXPR_LAMBDA auto safe_make_unsigned = [](auto t) {
- return hana::eval_if(hana::traits::is_integral(t),
- hana::make_lazy(hana::traits::make_unsigned)(t),
- hana::make_lazy(t)
- );
- };
- BOOST_HANA_CONSTANT_CHECK(safe_make_unsigned(hana::type_c<void>) == hana::type_c<void>);
- BOOST_HANA_CONSTANT_CHECK(safe_make_unsigned(hana::type_c<int>) == hana::type_c<unsigned int>);
- // eval_if with homogeneous branches and a constexpr or runtime condition
- BOOST_HANA_CONSTEXPR_LAMBDA auto safe_divide = [](auto x, auto y) {
- return hana::eval_if(y == 0,
- [=](auto) { return 0; },
- [=](auto _) { return _(x) / y; }
- );
- };
- int main() {
- BOOST_HANA_CONSTEXPR_CHECK(safe_divide(6, 3) == 2);
- BOOST_HANA_CONSTEXPR_CHECK(safe_divide(6, 0) == 0);
- }
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