ceph/src/boost/boost/callable_traits/function_type.hpp

   1 /*
   2
   3 @Copyright Barrett Adair 2015-2017
   4 Distributed under the Boost Software License, Version 1.0.
   5 (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
   6
   7 */
   8
   9 #ifndef BOOST_CLBL_TRTS_FUNCTION_TYPE_HPP
  10 #define BOOST_CLBL_TRTS_FUNCTION_TYPE_HPP
  11
  12 #include <boost/callable_traits/detail/core.hpp>
  13
  14 namespace boost { namespace callable_traits {
  15
  16 //[ function_type_hpp
  17 /*`[section:ref_function_type function_type]
  18 [heading Header]
  19 ``#include <boost/callable_traits/function_type.hpp>``
  20 [heading Definition]
  21 */
  22
  23 template<typename T>
  24 using function_type_t = //see below
  25 //<-
  26     detail::try_but_fail_if_invalid<typename detail::traits<
  27             detail::shallow_decay<T>>::function_type,
  28         cannot_determine_parameters_for_this_type>;
  29
  30 namespace detail {
  31
  32     template<typename T, typename = std::false_type>
  33     struct function_type_impl {};
  34
  35     template<typename T>
  36     struct function_type_impl <T, typename std::is_same<
  37         function_type_t<T>, detail::dummy>::type>
  38     {
  39         using type = function_type_t<T>;
  40     };
  41 }
  42
  43 //->
  44
  45 template<typename T>
  46 struct function_type : detail::function_type_impl<T> {};
  47
  48 //<-
  49 }} // namespace boost::callable_traits
  50 //->
  51
  52 /*`
  53 [heading Constraints]
  54 * `T` must be one of the following:
  55   * function
  56   * function pointer
  57   * function reference
  58   * member function pointer
  59   * member data pointer
  60   * user-defined type with a non-overloaded `operator()`
  61   * type of a non-generic lambda
  62
  63 [heading Behavior]
  64 * When the constraints are violated, a substitution failure occurs.
  65 * When `T` is a function, the aliased type is identical to `T`, except that the aliased function type will not have member qualifiers or the `transaction_safe` specifier.
  66 * When `T` is a function pointer, the aliased type is equivalent to `std::remove_pointer_t<T>`.
  67 * When `T` is a function reference, the aliased type is equivalent to `std::remove_reference_t<T>`.
  68 * When `T` is a function object, the aliased type is a function type with the same return type and parameter list as `T`'s `operator()`.
  69 * When `T` is a member function pointer, the aliased type is a function type with the same return type as `T`, and the first parameter is a reference to the parent class of `T`, qualified according to the member qualifiers on `T`. The subsequent parameters, if any, are the parameter types of `T`.
  70 * When `T` is a member data pointer, the aliased type is a function type returning the underlying member type of `T`, taking a single parameter, which is a `const` reference to the parent type of `T`.
  71 * In all cases, the aliased function type will not have member qualifiers, and will not have the `transaction_safe` specifier.
  72
  73 [heading Input/Output Examples]
  74 [table
  75     [[`T`]                              [`function_type_t<T>`]]
  76     [[`void(int)`]                      [`void(int)`]]
  77     [[`void(int) const`]                [`void(int)`]]
  78     [[`void(int) transaction_safe`]     [`void(int)`]]
  79     [[`void(*const &)(int)`]            [`void(int)`]]
  80     [[`void(&)(int)`]                   [`void(int)`]]
  81     [[`void(* volatile)()`]             [`void()`]]
  82     [[`int(foo::*)(int)`]               [`int(foo&, int)`]]
  83     [[`int(foo::*)(int) const`]         [`int(const foo&, int)`]]
  84     [[`void(foo::*)() volatile &&`]     [`void(volatile foo&&)`]]
  85     [[`int foo::*`]                     [`int(const foo&)`]]
  86     [[`const int foo::*`]               [`int(const foo&)`]]
  87     [[`int`]                            [(substitution failure)]]
  88 ]
  89
  90 [heading Example Program]
  91 [import ../example/function_type.cpp]
  92 [function_type]
  93 [endsect]
  94 */
  95 //]
  96
  97 #endif