ceph/src/boost/libs/hana/example/slice.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/core/to.hpp>
   7 #include <boost/hana/equal.hpp>
   8 #include <boost/hana/filter.hpp>
   9 #include <boost/hana/integral_constant.hpp>
  10 #include <boost/hana/length.hpp>
  11 #include <boost/hana/mod.hpp>
  12 #include <boost/hana/range.hpp>
  13 #include <boost/hana/slice.hpp>
  14 #include <boost/hana/tuple.hpp>
  15 #include <boost/hana/type.hpp>
  16 namespace hana = boost::hana;
  17 using namespace hana::literals;
  18
  19
  20 // Slice a contiguous range
  21 constexpr auto xs = hana::make_tuple(0, '1', 2.2, 3_c, hana::type_c<float>);
  22
  23 static_assert(
  24     hana::slice(xs, hana::tuple_c<std::size_t, 1, 2, 3>) ==
  25     hana::make_tuple('1', 2.2, 3_c)
  26 , "");
  27
  28
  29 // A more complex example with a non-contiguous range
  30 constexpr auto letters = hana::to_tuple(hana::range_c<char, 'a', 'z'>);
  31 constexpr auto indices = hana::to_tuple(hana::make_range(hana::size_c<0>, hana::length(letters)));
  32
  33 auto even_indices = hana::filter(indices, [](auto n) {
  34     return n % hana::size_c<2> == hana::size_c<0>;
  35 });
  36
  37 BOOST_HANA_CONSTANT_CHECK(
  38     hana::slice(letters, even_indices) == hana::tuple_c<char,
  39         'a', 'c', 'e', 'g', 'i', 'k', 'm', 'o', 'q', 's', 'u', 'w', 'y'
  40     >
  41 );
  42
  43 int main() { }