ceph/src/boost/libs/hana/example/integral_constant.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/config.hpp>
   7 #include <boost/hana/equal.hpp>
   8 #include <boost/hana/for_each.hpp>
   9 #include <boost/hana/integral_constant.hpp>
  10 #include <boost/hana/mult.hpp>
  11 #include <boost/hana/negate.hpp>
  12 #include <boost/hana/plus.hpp>
  13 #include <boost/hana/tuple.hpp>
  14
  15 #include <string>
  16 #include <vector>
  17 namespace hana = boost::hana;
  18
  19
  20 int main() {
  21
  22 {
  23
  24 //! [operators]
  25 BOOST_HANA_CONSTANT_CHECK(hana::int_c<1> + hana::int_c<3> == hana::int_c<4>);
  26
  27 // Mixed-type operations are supported, but only when it involves a
  28 // promotion, and not a conversion that could be lossy.
  29 BOOST_HANA_CONSTANT_CHECK(hana::size_c<3> * hana::ushort_c<5> == hana::size_c<15>);
  30 BOOST_HANA_CONSTANT_CHECK(hana::llong_c<15> == hana::int_c<15>);
  31 //! [operators]
  32
  33 }{
  34
  35 //! [times_loop_unrolling]
  36 std::string s;
  37 for (char c = 'x'; c <= 'z'; ++c)
  38     hana::int_<5>::times([&] { s += c; });
  39
  40 BOOST_HANA_RUNTIME_CHECK(s == "xxxxxyyyyyzzzzz");
  41 //! [times_loop_unrolling]
  42
  43 }{
  44
  45 //! [times_higher_order]
  46 std::string s;
  47 auto functions = hana::make_tuple(
  48     [&] { s += "x"; },
  49     [&] { s += "y"; },
  50     [&] { s += "z"; }
  51 );
  52 hana::for_each(functions, hana::int_<5>::times);
  53 BOOST_HANA_RUNTIME_CHECK(s == "xxxxxyyyyyzzzzz");
  54 //! [times_higher_order]
  55
  56 }{
  57
  58 //! [from_object]
  59 std::string s;
  60 for (char c = 'x'; c <= 'z'; ++c)
  61     hana::int_c<5>.times([&] { s += c; });
  62
  63 BOOST_HANA_RUNTIME_CHECK(s == "xxxxxyyyyyzzzzz");
  64 //! [from_object]
  65
  66 }{
  67
  68 //! [times_with_index_runtime]
  69 std::vector<int> v;
  70 hana::int_<5>::times.with_index([&](auto index) { v.push_back(index); });
  71
  72 BOOST_HANA_RUNTIME_CHECK(v == std::vector<int>{0, 1, 2, 3, 4});
  73 //! [times_with_index_runtime]
  74
  75 //! [times_with_index_compile_time]
  76 constexpr auto xs = hana::tuple_c<int, 0, 1, 2>;
  77 hana::int_<3>::times.with_index([xs](auto index) {
  78     BOOST_HANA_CONSTANT_CHECK(xs[index] == index);
  79 });
  80 //! [times_with_index_compile_time]
  81
  82 }{
  83
  84 //! [literals]
  85 using namespace hana::literals; // contains the _c suffix
  86
  87 BOOST_HANA_CONSTANT_CHECK(1234_c == hana::llong_c<1234>);
  88 BOOST_HANA_CONSTANT_CHECK(-1234_c == hana::llong_c<-1234>);
  89 BOOST_HANA_CONSTANT_CHECK(1_c + (3_c * 4_c) == hana::llong_c<1 + (3 * 4)>);
  90 //! [literals]
  91
  92 }{
  93
  94 //! [integral_c]
  95 BOOST_HANA_CONSTANT_CHECK(hana::integral_c<int, 2> == hana::int_c<2>);
  96 static_assert(decltype(hana::integral_c<int, 2>)::value == 2, "");
  97 //! [integral_c]
  98
  99 }
 100
 101 }