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43 lines
1.3 KiB
C++
43 lines
1.3 KiB
C++
/*
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@copyright Louis Dionne 2014
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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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*/
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//////////////////////////////////////////////////////////////////////////////
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// Important: Keep this file in sync with the Overview in the README
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//////////////////////////////////////////////////////////////////////////////
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#include <boost/hana/assert.hpp>
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#include <boost/hana/tuple.hpp>
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#include <boost/hana/type.hpp>
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#include <string>
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using namespace boost::hana;
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struct President { std::string name; };
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struct Car { std::string name; };
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struct City { std::string name; };
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int main() {
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// Heterogeneous sequences for value-level metaprogramming.
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auto stuff = tuple(President{"Obama"}, Car{"Toyota"}, City{"Quebec"});
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auto names = transform(stuff, [](auto thing) { return thing.name; });
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BOOST_HANA_RUNTIME_CHECK(reverse(names) == tuple("Quebec", "Toyota", "Obama"));
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// No compile-time information is lost:
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// `stuff` wasn't constexpr but its length is!
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static_assert(length(stuff) == 3u, "");
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// Type-level metaprogramming works too.
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auto types = transform(stuff, [](auto thing) {
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return type<decltype(thing)*>;
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});
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BOOST_HANA_CONSTANT_CHECK(
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types == tuple(type<President*>, type<Car*>, type<City*>)
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);
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}
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