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81 lines
1.8 KiB
C++
81 lines
1.8 KiB
C++
/*
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@copyright Louis Dionne 2015
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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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#include <boost/hana/assert.hpp>
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#include <boost/hana/config.hpp>
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#include <boost/hana/integral_constant.hpp>
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#include <boost/hana/maybe.hpp>
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#include <boost/hana/tuple.hpp>
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using namespace boost::hana;
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int main() {
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{
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//! [sequence]
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BOOST_HANA_CONSTEXPR_CHECK(
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sequence<Maybe>(make<Tuple>(just(1), just('2'), just(3.3))) ==
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just(make<Tuple>(1, '2', 3.3))
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);
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BOOST_HANA_CONSTANT_CHECK(
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sequence<Maybe>(make<Tuple>(just(1), nothing, just(3.3))) == nothing
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);
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// This is a generalized Cartesian product.
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BOOST_HANA_CONSTEXPR_CHECK(
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sequence<Tuple>(make<Tuple>(make<Tuple>(1, 2, 3),
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make<Tuple>(4),
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make<Tuple>(5, 6)))
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==
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make<Tuple>(
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make<Tuple>(1, 4, 5), make<Tuple>(1, 4, 6),
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make<Tuple>(2, 4, 5), make<Tuple>(2, 4, 6),
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make<Tuple>(3, 4, 5), make<Tuple>(3, 4, 6)
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)
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);
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//! [sequence]
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}{
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//! [traverse]
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BOOST_HANA_CONSTEXPR_LAMBDA auto half = [](auto x) {
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return if_(x % int_<2> == int_<0>,
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just(x / int_<2>),
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nothing
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);
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};
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BOOST_HANA_CONSTANT_CHECK(
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traverse<Maybe>(make<Tuple>(int_<2>, int_<4>, int_<6>), half)
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==
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just(make<Tuple>(int_<1>, int_<2>, int_<3>))
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);
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BOOST_HANA_CONSTANT_CHECK(
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traverse<Maybe>(make<Tuple>(int_<2>, int_<3>, int_<6>), half)
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==
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nothing
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);
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BOOST_HANA_CONSTEXPR_LAMBDA auto twice = [](auto x) {
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return make<Tuple>(x, x);
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};
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BOOST_HANA_CONSTEXPR_CHECK(
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traverse<Tuple>(just('x'), twice) == make<Tuple>(just('x'), just('x'))
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);
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BOOST_HANA_CONSTANT_CHECK(
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traverse<Tuple>(nothing, twice) == make<Tuple>(nothing)
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);
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//! [traverse]
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}
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}
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