ceph/src/boost/libs/hana/example/tap.cpp

   1 // Copyright Louis Dionne 2013-2016
   2 // Distributed under the Boost Software License, Version 1.0.
   3 // (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
   4
   5 #include <boost/hana/assert.hpp>
   6 #include <boost/hana/chain.hpp>
   7 #include <boost/hana/equal.hpp>
   8 #include <boost/hana/tap.hpp>
   9 #include <boost/hana/tuple.hpp>
  10
  11 #include <set>
  12 namespace hana = boost::hana;
  13
  14
  15 int main() {
  16     // We use a sorted container because the order in which the functions
  17     // are called is unspecified.
  18     std::set<int> before, after;
  19
  20     auto xs = hana::make_tuple(1, 2, 3)
  21         | hana::tap<hana::tuple_tag>([&](int x) { before.insert(x); })
  22         | [](auto x) { return hana::make_tuple(x, -x); }
  23         | hana::tap<hana::tuple_tag>([&](int x) { after.insert(x); });
  24
  25     BOOST_HANA_RUNTIME_CHECK(before == std::set<int>{1, 2, 3});
  26     BOOST_HANA_RUNTIME_CHECK(after == std::set<int>{1, -1, 2, -2, 3, -3});
  27     BOOST_HANA_RUNTIME_CHECK(xs == hana::make_tuple(1, -1, 2, -2, 3, -3));
  28 }