ceph/src/boost/libs/hana/example/filter.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/assert.hpp>
   6 #include <boost/hana/equal.hpp>
   7 #include <boost/hana/ext/std/integral_constant.hpp>
   8 #include <boost/hana/filter.hpp>
   9 #include <boost/hana/functional/compose.hpp>
  10 #include <boost/hana/optional.hpp>
  11 #include <boost/hana/tuple.hpp>
  12 #include <boost/hana/type.hpp>
  13
  14 #include <type_traits>
  15 namespace hana = boost::hana;
  16
  17
  18 // First take the type of an object, and then tell whether it's integral
  19 constexpr auto is_integral = hana::compose(hana::trait<std::is_integral>, hana::typeid_);
  20
  21 static_assert(hana::filter(hana::make_tuple(1, 2.0, 3, 4.0), is_integral) == hana::make_tuple(1, 3), "");
  22 static_assert(hana::filter(hana::just(3), is_integral) == hana::just(3), "");
  23 BOOST_HANA_CONSTANT_CHECK(hana::filter(hana::just(3.0), is_integral) == hana::nothing);
  24
  25 int main() { }