ceph/src/boost/libs/hana/example/find_if.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/equal.hpp>
   7 #include <boost/hana/equal.hpp>
   8 #include <boost/hana/ext/std/integral_constant.hpp>
   9 #include <boost/hana/find_if.hpp>
  10 #include <boost/hana/functional/compose.hpp>
  11 #include <boost/hana/optional.hpp>
  12 #include <boost/hana/tuple.hpp>
  13 #include <boost/hana/type.hpp>
  14
  15 #include <type_traits>
  16 namespace hana = boost::hana;
  17
  18
  19 // First get the type of the object, and then call the trait on it.
  20 constexpr auto is_integral = hana::compose(hana::trait<std::is_integral>, hana::typeid_);
  21 constexpr auto is_class = hana::compose(hana::trait<std::is_class>, hana::typeid_);
  22
  23 static_assert(
  24     hana::find_if(hana::make_tuple(1.0, 2, '3'), is_integral) == hana::just(2)
  25 , "");
  26
  27 BOOST_HANA_CONSTANT_CHECK(
  28     hana::find_if(hana::make_tuple(1.0, 2, '3'), is_class) == hana::nothing
  29 );
  30
  31 constexpr auto types = hana::tuple_t<char, int, unsigned, long, unsigned long>;
  32 BOOST_HANA_CONSTANT_CHECK(
  33     hana::find_if(types, hana::equal.to(hana::type_c<unsigned>)) == hana::just(hana::type_c<unsigned>)
  34 );
  35 BOOST_HANA_CONSTANT_CHECK(
  36     hana::find_if(types, hana::equal.to(hana::type_c<void>)) == hana::nothing
  37 );
  38
  39 int main() { }