boost/callable_traits/apply_return.hpp

0001 /*
0002
0003 @Copyright Barrett Adair 2015-2017
0004 Distributed under the Boost Software License, Version 1.0.
0005 (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
0006
0007 */
0008
0009 #ifndef BOOST_CLBL_TRTS_APPLY_RETURN_HPP
0010 #define BOOST_CLBL_TRTS_APPLY_RETURN_HPP
0011
0012 #include <boost/callable_traits/detail/core.hpp>
0013
0014 namespace boost { namespace callable_traits {
0015
0016 BOOST_CLBL_TRTS_DEFINE_SFINAE_ERROR_ORIGIN(apply_return)
0017 BOOST_CLBL_TRTS_SFINAE_MSG(apply_return, invalid_types_for_apply_return)
0018
0019 namespace detail {
0020
0021     template<typename T, typename R>
0022     struct apply_return_helper {
0023         using type = typename detail::traits<T>::template apply_return<R>;
0024     };
0025
0026     //special case
0027     template<typename... Args, typename R>
0028     struct apply_return_helper<std::tuple<Args...>, R> {
0029         using type = R(Args...);
0030     };
0031 }
0032
0033 //[ apply_return_hpp
0034 /*`
0035 [section:ref_apply_return apply_return]
0036 [heading Header]
0037 ``#include <boost/callable_traits/apply_return.hpp>``
0038 [heading Definition]
0039 */
0040
0041 template<typename T, typename R>
0042 using apply_return_t = //see below
0043 //<-
0044     detail::try_but_fail_if_invalid<
0045         typename detail::apply_return_helper<T, R>::type,
0046         invalid_types_for_apply_return>;
0047
0048 namespace detail {
0049
0050     template<typename T, typename R, typename = std::false_type>
0051     struct apply_return_impl {};
0052
0053     template<typename T, typename R>
0054     struct apply_return_impl <T, R, typename std::is_same<
0055         apply_return_t<T, R>, detail::dummy>::type>
0056     {
0057         using type = apply_return_t<T, R>;
0058     };
0059 }
0060     //->
0061
0062 template<typename T, typename R>
0063 struct apply_return : detail::apply_return_impl<T, R> {};
0064
0065 //<-
0066 }} // namespace boost::callable_traits
0067 //->
0068
0069 /*`
0070 [heading Constraints]
0071 * `T` must one of the following:
0072   * `std::tuple` template instantiation
0073   * function
0074   * function pointer
0075   * function reference
0076   * member function pointer
0077   * member data pointer
0078 * If `T` is a pointer, it may not be cv/ref qualified
0079
0080 [heading Behavior]
0081 * When `T` is `std::tuple<Args...>`, the aliased type is `R(Args...)`.
0082 * When `T` is a function, function pointer, function reference, or member function pointer, the aliased type's return type is `R`, but is otherwise identical to `T`.
0083 * When `T` is a member data pointer of class `foo` to a `U` type (such that `T` is `U foo::*`), the aliased type is `R foo::*`.
0084
0085 [heading Input/Output Examples]
0086 [table
0087     [[`T`]                              [`apply_return_t<T, float>`]]
0088     [[`std::tuple<int, int>`]           [`float(int, int)`]]
0089     [[`int()`]                          [`float()`]]
0090     [[`int (&)()`]                      [`float(&)()`]]
0091     [[`int (*)()`]                      [`float(*)()`]]
0092     [[`int (*)(...)`]                   [`float(*)()`]]
0093     [[`int(foo::*)()`]                  [`float(foo::*)()`]]
0094     [[`int(foo::*)() &`]                [`float(foo::*)() &`]]
0095     [[`int(foo::*)() &&`]               [`float(foo::*)() &&`]]
0096     [[`int(foo::*)() const`]            [`float(foo::*)() const`]]
0097     [[`int(foo::*)() transaction_safe`] [`float(foo::*)() transaction_safe`]]
0098     [[`int foo::*`]                     [`float foo::*`]]
0099     [[`int`]                            [(substitution failure)]]
0100     [[`int (*const)()`]                 [(substitution failure)]]
0101 ]
0102
0103 [heading Example Program]
0104 [/import ../example/apply_return.cpp]
0105 [apply_return]
0106 [endsect]
0107 */
0108 //]
0109 #endif