hana/example/tap.cpp
2017-01-07 14:14:18 -08:00

29 lines
999 B
C++

// 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/chain.hpp>
#include <boost/hana/equal.hpp>
#include <boost/hana/tap.hpp>
#include <boost/hana/tuple.hpp>
#include <set>
namespace hana = boost::hana;
int main() {
// We use a sorted container because the order in which the functions
// are called is unspecified.
std::set<int> before, after;
auto xs = hana::make_tuple(1, 2, 3)
| hana::tap<hana::tuple_tag>([&](int x) { before.insert(x); })
| [](auto x) { return hana::make_tuple(x, -x); }
| hana::tap<hana::tuple_tag>([&](int x) { after.insert(x); });
BOOST_HANA_RUNTIME_CHECK(before == std::set<int>{1, 2, 3});
BOOST_HANA_RUNTIME_CHECK(after == std::set<int>{1, -1, 2, -2, 3, -3});
BOOST_HANA_RUNTIME_CHECK(xs == hana::make_tuple(1, -1, 2, -2, 3, -3));
}