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84 lines
2.0 KiB
C++
84 lines
2.0 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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#include <boost/hana/assert.hpp>
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#include <boost/hana/bool.hpp>
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#include <boost/hana/detail/constexpr.hpp>
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#include <boost/hana/maybe.hpp>
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#include <boost/hana/tuple.hpp>
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#include <boost/hana/type.hpp>
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#include <sstream>
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using namespace boost::hana;
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int main() {
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{
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//! [flatten]
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BOOST_HANA_CONSTEXPR_CHECK(
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flatten(tuple(tuple(1, 2, 3), tuple(4, 5), tuple(6, 7, 8, 9)))
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==
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tuple(1, 2, 3, 4, 5, 6, 7, 8, 9)
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);
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BOOST_HANA_CONSTANT_CHECK(flatten(nothing) == nothing);
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BOOST_HANA_CONSTEXPR_CHECK(flatten(just(just(1))) == just(1));
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BOOST_HANA_CONSTANT_CHECK(flatten(just(nothing)) == nothing);
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//! [flatten]
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}{
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//! [mcompose]
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BOOST_HANA_CONSTEXPR_LAMBDA auto block = [](auto ...types) {
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return [=](auto x) {
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return if_(elem(tuple(types...), decltype_(x)),
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nothing,
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just(x)
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);
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};
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};
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BOOST_HANA_CONSTEXPR_LAMBDA auto f = block(type<double>);
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BOOST_HANA_CONSTEXPR_LAMBDA auto g = block(type<int>);
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BOOST_HANA_CONSTEXPR_LAMBDA auto h = mcompose<Maybe>(f, g);
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BOOST_HANA_CONSTANT_CHECK(h(1) == nothing); // fails inside g; 1 has type int
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BOOST_HANA_CONSTANT_CHECK(h(1.2) == nothing); // fails inside f; 1.2 has type double
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BOOST_HANA_CONSTEXPR_CHECK(h('x') == just('x')); // ok; 'x' has type char
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//! [mcompose]
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}{
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//! [then]
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struct undefined { };
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BOOST_HANA_CONSTEXPR_CHECK(
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then(tuple(undefined{}, undefined{}), tuple(1, 2, 3)) == tuple(
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1, 2, 3,
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1, 2, 3
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)
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);
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//! [then]
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}{
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//! [tap]
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std::stringstream before, after;
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auto xs = tuple(1, 2, 3)
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| tap<Tuple>([&](auto x) { before << x << ' '; })
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| [](auto x) { return tuple(x, -x); }
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| tap<Tuple>([&](auto x) { after << x << ' '; });
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BOOST_HANA_RUNTIME_CHECK(before.str() == "1 2 3 ");
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BOOST_HANA_RUNTIME_CHECK(after.str() == "1 -1 2 -2 3 -3 ");
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BOOST_HANA_RUNTIME_CHECK(xs == tuple(1, -1, 2, -2, 3, -3));
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//! [tap]
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}
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}
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