ceph/src/boost/libs/hana/example/functional/on.cpp

   1 // Copyright Louis Dionne 2013-2017
   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/first.hpp>
   6 #include <boost/hana/functional/on.hpp>
   7 #include <boost/hana/integral_constant.hpp>
   8 #include <boost/hana/less.hpp>
   9 #include <boost/hana/pair.hpp>
  10 #include <boost/hana/plus.hpp>
  11 #include <boost/hana/sort.hpp>
  12 #include <boost/hana/tuple.hpp>
  13 #include <boost/hana/type.hpp>
  14 namespace hana = boost::hana;
  15
  16
  17 // infix application
  18 constexpr auto sorted = hana::sort.by(hana::less ^hana::on^ hana::first, hana::make_tuple(
  19     hana::make_pair(hana::int_c<3>, 'x'),
  20     hana::make_pair(hana::int_c<1>, hana::type_c<void>),
  21     hana::make_pair(hana::int_c<2>, 9876)
  22 ));
  23
  24 static_assert(sorted == hana::make_tuple(
  25     hana::make_pair(hana::int_c<1>, hana::type_c<void>),
  26     hana::make_pair(hana::int_c<2>, 9876),
  27     hana::make_pair(hana::int_c<3>, 'x')
  28 ), "");
  29
  30
  31 // function call syntax
  32 constexpr auto x = hana::make_pair(1, 2);
  33 constexpr auto y = hana::make_pair(10, 20);
  34 static_assert(hana::on(hana::plus, hana::first)(x, y) == 1 + 10, "");
  35
  36 int main() { }