/*
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@Copyright Barrett Adair 2015-2017
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
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*/
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#ifndef BOOST_CLBL_TRTS_HAS_VOID_RETURN_HPP
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#define BOOST_CLBL_TRTS_HAS_VOID_RETURN_HPP
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#include <boost/callable_traits/detail/core.hpp>
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namespace boost { namespace callable_traits {
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//[ has_void_return_hpp
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/*`[section:ref_has_void_return has_void_return]
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[heading Header]
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``#include <boost/callable_traits/has_void_return.hpp>``
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[heading Definition]
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*/
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// inherits from either std::true_type or std::false_type
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template<typename T>
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struct has_void_return;
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//<-
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template<typename T>
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struct has_void_return
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: std::is_same<typename detail::traits<
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detail::shallow_decay<T>>::return_type, void> {};
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#ifdef BOOST_CLBL_TRTS_DISABLE_VARIABLE_TEMPLATES
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template<typename T>
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struct has_void_return_v {
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static_assert(std::is_same<T, detail::dummy>::value,
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"Variable templates not supported on this compiler.");
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};
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#else
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//->
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// only available when variable templates are supported
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template<typename T>
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//<-
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BOOST_CLBL_TRAITS_INLINE_VAR
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//->
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constexpr bool has_void_return_v = //see below
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//<-
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std::is_same<typename detail::traits<
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detail::shallow_decay<T>>::return_type, void>::value;
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#endif
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}} // namespace boost::callable_traits
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//->
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/*`
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[heading Constraints]
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* none
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[heading Behavior]
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* `std::false_type` is inherited by `has_void_return<T>` and is aliased by `typename has_void_return<T>::type`, except when one of the following criteria is met, in which case `std::true_type` would be similarly inherited and aliased:
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* `T` is a function, function pointer, or function reference where the function's return type is `void`.
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* `T` is a pointer to a member function whose return type is `void`.
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* `T` is a function object with a non-overloaded `operator()`, where the `operator()` function returns `void`.
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* On compilers that support variable templates, `has_void_return_v<T>` is equivalent to `has_void_return<T>::value`.
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[heading Input/Output Examples]
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[table
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[[`T`] [`has_void_return_v<T>`]]
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[[`void()`] [`true`]]
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[[`void(int) const`] [`true`]]
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[[`void(* const &)()`] [`true`]]
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[[`void(&)()`] [`true`]]
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[[`void(foo::*)() const`] [`true`]]
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[[`int(*)()`] [`false`]]
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[[`int(*&)()`] [`false`]]
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[[`int`] [`false`]]
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[[`int foo::*`] [`false`]]
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[[`void* foo::*`] [`false`]]
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]
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[heading Example Program]
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[import ../example/has_void_return.cpp]
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[has_void_return]
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[endsect]
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*/
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//]
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#endif
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