ceph/src/boost/libs/hana/example/while.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/integral_constant.hpp>
   8 #include <boost/hana/less.hpp>
   9 #include <boost/hana/plus.hpp>
  10 #include <boost/hana/while.hpp>
  11
  12 #include <vector>
  13 namespace hana = boost::hana;
  14 using namespace hana::literals;
  15
  16
  17 int main() {
  18     // while_ with a Constant condition (loop is unrolled at compile-time)
  19     {
  20         std::vector<int> ints;
  21         auto final_state = hana::while_(hana::less.than(10_c), 0_c, [&](auto i) {
  22             ints.push_back(i);
  23             return i + 1_c;
  24         });
  25
  26         // The state is known at compile-time
  27         BOOST_HANA_CONSTANT_CHECK(final_state == 10_c);
  28
  29         BOOST_HANA_RUNTIME_CHECK(ints == std::vector<int>{0, 1, 2, 3, 4, 5, 6, 7, 8, 9});
  30     }
  31
  32     // while_ with a constexpr or runtime condition (loop is not unrolled)
  33     {
  34         std::vector<int> ints;
  35         int final_state = hana::while_(hana::less.than(10), 0, [&](int i) {
  36             ints.push_back(i);
  37             return i + 1;
  38         });
  39
  40         // The state is known only at runtime, or at compile-time if constexpr
  41         BOOST_HANA_RUNTIME_CHECK(final_state == 10);
  42
  43         BOOST_HANA_RUNTIME_CHECK(ints == std::vector<int>{0, 1, 2, 3, 4, 5, 6, 7, 8, 9});
  44     }
  45 }