ceph/src/boost/libs/hana/test/type/metafunction.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/concept/metafunction.hpp>
   7 #include <boost/hana/equal.hpp>
   8 #include <boost/hana/type.hpp>
   9
  10 #include <type_traits>
  11 namespace hana = boost::hana;
  12
  13
  14 struct x1; struct x2; struct x3;
  15 struct y1 { }; struct y2 { }; struct y3 { };
  16 template <typename ...> struct f { struct type; };
  17
  18 template <typename F, typename ...T>
  19 constexpr auto valid_call(F f, T ...t) -> decltype(((void)f(t...)), true)
  20 { return true; }
  21 constexpr auto valid_call(...)
  22 { return false; }
  23
  24 BOOST_HANA_CONSTANT_CHECK(hana::equal(
  25     hana::metafunction<f>(),
  26     hana::type_c<f<>::type>
  27 ));
  28
  29 BOOST_HANA_CONSTANT_CHECK(hana::equal(
  30     hana::metafunction<f>(hana::type_c<x1>),
  31     hana::type_c<f<x1>::type>
  32 ));
  33
  34 BOOST_HANA_CONSTANT_CHECK(hana::equal(
  35     hana::metafunction<f>(hana::type_c<x1>, hana::type_c<x2>),
  36     hana::type_c<f<x1, x2>::type>
  37 ));
  38
  39 BOOST_HANA_CONSTANT_CHECK(hana::equal(
  40     hana::metafunction<f>(hana::type_c<x1>, hana::type_c<x2>, hana::type_c<x3>),
  41     hana::type_c<f<x1, x2, x3>::type>
  42 ));
  43
  44 using F = decltype(hana::metafunction<f>);
  45 static_assert(std::is_same<F::apply<>, f<>>::value, "");
  46 static_assert(std::is_same<F::apply<x1>, f<x1>>::value, "");
  47 static_assert(std::is_same<F::apply<x1, x2>, f<x1, x2>>::value, "");
  48 static_assert(std::is_same<F::apply<x1, x2, x3>, f<x1, x2, x3>>::value, "");
  49
  50 // Make sure we're SFINAE-friendly
  51 template <typename ...T> struct no_type { };
  52 static_assert(!valid_call(hana::metafunction<no_type>), "");
  53 static_assert(!valid_call(hana::metafunction<no_type>, hana::type_c<x1>), "");
  54
  55 // Make sure we model the Metafunction concept
  56 static_assert(hana::Metafunction<decltype(hana::metafunction<f>)>::value, "");
  57 static_assert(hana::Metafunction<decltype(hana::metafunction<f>)&>::value, "");
  58
  59
  60 // Make sure we don't read from a non-constexpr variable
  61 int main() {
  62     auto t = hana::type_c<x1>;
  63     constexpr auto r = hana::metafunction<f>(t);
  64     (void)r;
  65 }