39 lines
1.3 KiB
C++
39 lines
1.3 KiB
C++
// Copyright Louis Dionne 2013-2017
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// Distributed under the Boost Software License, Version 1.0.
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// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
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#include <boost/hana/assert.hpp>
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#include <boost/hana/config.hpp>
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#include <boost/hana/equal.hpp>
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#include <boost/hana/eval_if.hpp>
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#include <boost/hana/lazy.hpp>
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#include <boost/hana/traits.hpp>
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#include <boost/hana/type.hpp>
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namespace hana = boost::hana;
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// eval_if with heterogeneous branches and a Constant condition
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BOOST_HANA_CONSTEXPR_LAMBDA auto safe_make_unsigned = [](auto t) {
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return hana::eval_if(hana::traits::is_integral(t),
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hana::make_lazy(hana::traits::make_unsigned)(t),
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hana::make_lazy(t)
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);
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};
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BOOST_HANA_CONSTANT_CHECK(safe_make_unsigned(hana::type_c<void>) == hana::type_c<void>);
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BOOST_HANA_CONSTANT_CHECK(safe_make_unsigned(hana::type_c<int>) == hana::type_c<unsigned int>);
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// eval_if with homogeneous branches and a constexpr or runtime condition
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BOOST_HANA_CONSTEXPR_LAMBDA auto safe_divide = [](auto x, auto y) {
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return hana::eval_if(y == 0,
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[=](auto) { return 0; },
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[=](auto _) { return _(x) / y; }
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);
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};
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int main() {
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BOOST_HANA_CONSTEXPR_CHECK(safe_divide(6, 3) == 2);
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BOOST_HANA_CONSTEXPR_CHECK(safe_divide(6, 0) == 0);
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}
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