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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/first.hpp>
#include <boost/hana/fold_left.hpp>
#include <boost/hana/insert.hpp>
#include <boost/hana/integral_constant.hpp>
#include <boost/hana/map.hpp>
#include <boost/hana/pair.hpp>
#include <boost/hana/second.hpp>
#include <boost/hana/type.hpp>
namespace hana = boost::hana;
int main() {
// Given a map of (key, value) pairs, returns a map of (value, key) pairs.
// This requires both the keys and the values to be compile-time Comparable.
auto invert = [](auto map) {
return hana::fold_left(map, hana::make_map(), [](auto map, auto pair) {
return hana::insert(map, hana::make_pair(hana::second(pair), hana::first(pair)));
});
};
auto m = hana::make_map(
hana::make_pair(hana::type_c<int>, hana::int_c<1>),
hana::make_pair(hana::type_c<float>, hana::int_c<2>),
hana::make_pair(hana::int_c<3>, hana::type_c<void>)
);
BOOST_HANA_CONSTANT_CHECK(invert(m) ==
hana::make_map(
hana::make_pair(hana::int_c<1>, hana::type_c<int>),
hana::make_pair(hana::int_c<2>, hana::type_c<float>),
hana::make_pair(hana::type_c<void>, hana::int_c<3>)
)
);
}
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