ceph/src/boost/libs/callable_traits/example/intro.cpp

   1 /*<-
   2 Copyright Barrett Adair 2016-2017
   3 Distributed under the Boost Software License, Version 1.0.
   4 (See accompanying file LICENSE.md or copy at http ://boost.org/LICENSE_1_0.txt)
   5 ->*/
   6
   7 #include <boost/callable_traits/detail/config.hpp>
   8 #ifdef BOOST_CLBL_TRTS_DISABLE_VARIABLE_TEMPLATES
   9 int main(){ return 0; }
  10 #else
  11
  12 //[ intro
  13 #include <type_traits>
  14 #include <tuple>
  15 #include <boost/callable_traits.hpp>
  16
  17 namespace ct = boost::callable_traits;
  18
  19 // This function template helps keep our example code neat
  20 template<typename A, typename B>
  21 void assert_same(){ static_assert(std::is_same<A, B>::value, ""); }
  22
  23 // foo is a function object
  24 struct foo {
  25     void operator()(int, char, float) const {}
  26 };
  27
  28 int main() {
  29
  30     // Use args_t to retrieve a parameter list as a std::tuple:
  31     assert_same<
  32         ct::args_t<foo>,
  33         std::tuple<int, char, float>
  34     >();
  35
  36     // has_void_return lets us perform a quick check for a void return type
  37     static_assert(ct::has_void_return<foo>::value, "");
  38
  39     // Detect C-style variadics (ellipses) in a signature (e.g. printf)
  40     static_assert(!ct::has_varargs<foo>::value, "");
  41
  42     // pmf is a pointer-to-member function: void (foo::*)(int, char, float) const
  43     using pmf = decltype(&foo::operator());
  44
  45     // remove_member_const_t lets you remove the const member qualifier
  46     assert_same<
  47         ct::remove_member_const_t<pmf>,
  48         void (foo::*)(int, char, float) /*no const!*/
  49     >();
  50
  51     // Conversely, add_member_const_t adds a const member qualifier
  52     assert_same<
  53         pmf,
  54         ct::add_member_const_t<void (foo::*)(int, char, float)>
  55     >();
  56
  57     // is_const_member_v checks for the presence of member const
  58     static_assert(ct::is_const_member<pmf>::value, "");
  59 }
  60
  61 //]
  62 #endif