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hyperrogue/mingw.invoke.h

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/// \file mingw.invoke.h
/// \brief Lightweight `invoke` implementation, for C++11 and C++14.
///
/// (c) 2018-2019 by Nathaniel J. McClatchey, San Jose, CA, United States
/// \author Nathaniel J. McClatchey, PhD
///
/// \copyright Simplified (2-clause) BSD License.
///
/// \note This file may become part of the mingw-w64 runtime package. If/when
/// this happens, the appropriate license will be added, i.e. this code will
/// become dual-licensed, and the current BSD 2-clause license will stay.
#ifndef MINGW_INVOKE_H_
#define MINGW_INVOKE_H_
#include <type_traits> // For std::result_of, etc.
#include <utility> // For std::forward
#include <functional> // For std::reference_wrapper
namespace mingw_stdthread
{
namespace detail
{
// For compatibility, implement std::invoke for C++11 and C++14
#if __cplusplus < 201703L
template<bool PMemFunc, bool PMemData>
struct Invoker
{
template<class F, class... Args>
inline static typename std::result_of<F(Args...)>::type invoke (F&& f, Args&&... args)
{
return std::forward<F>(f)(std::forward<Args>(args)...);
}
};
template<bool>
struct InvokerHelper;
template<>
struct InvokerHelper<false>
{
template<class T1>
inline static auto get (T1&& t1) -> decltype(*std::forward<T1>(t1))
{
return *std::forward<T1>(t1);
}
template<class T1>
inline static auto get (const std::reference_wrapper<T1>& t1) -> decltype(t1.get())
{
return t1.get();
}
};
template<>
struct InvokerHelper<true>
{
template<class T1>
inline static auto get (T1&& t1) -> decltype(std::forward<T1>(t1))
{
return std::forward<T1>(t1);
}
};
template<>
struct Invoker<true, false>
{
template<class T, class F, class T1, class... Args>
inline static auto invoke (F T::* f, T1&& t1, Args&&... args) ->\
decltype((InvokerHelper<std::is_base_of<T,typename std::decay<T1>::type>::value>::get(std::forward<T1>(t1)).*f)(std::forward<Args>(args)...))
{
return (InvokerHelper<std::is_base_of<T,typename std::decay<T1>::type>::value>::get(std::forward<T1>(t1)).*f)(std::forward<Args>(args)...);
}
};
template<>
struct Invoker<false, true>
{
template<class T, class F, class T1, class... Args>
inline static auto invoke (F T::* f, T1&& t1, Args&&... args) ->\
decltype(InvokerHelper<std::is_base_of<T,typename std::decay<T1>::type>::value>::get(t1).*f)
{
return InvokerHelper<std::is_base_of<T,typename std::decay<T1>::type>::value>::get(t1).*f;
}
};
template<class F, class... Args>
struct InvokeResult
{
typedef Invoker<std::is_member_function_pointer<typename std::remove_reference<F>::type>::value,
std::is_member_object_pointer<typename std::remove_reference<F>::type>::value &&
(sizeof...(Args) == 1)> invoker;
inline static auto invoke (F&& f, Args&&... args) -> decltype(invoker::invoke(std::forward<F>(f), std::forward<Args>(args)...))
{
return invoker::invoke(std::forward<F>(f), std::forward<Args>(args)...);
}
};
template<class F, class...Args>
auto invoke (F&& f, Args&&... args) -> decltype(InvokeResult<F, Args...>::invoke(std::forward<F>(f), std::forward<Args>(args)...))
{
return InvokeResult<F, Args...>::invoke(std::forward<F>(f), std::forward<Args>(args)...);
}
#else
using std::invoke;
#endif
} // Namespace "detail"
} // Namespace "mingw_stdthread"
#endif