sol2/sol/traits.hpp

// The MIT License (MIT)

// Copyright (c) 2013 Danny Y., Rapptz

// Permission is hereby granted, free of charge, to any person obtaining a copy of
// this software and associated documentation files (the "Software"), to deal in
// the Software without restriction, including without limitation the rights to
// use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
// the Software, and to permit persons to whom the Software is furnished to do so,
// subject to the following conditions:

// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
// FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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#ifndef SOL_TRAITS_HPP
#define SOL_TRAITS_HPP

#include <type_traits>

namespace sol {
template<typename T, typename R = void>
using EnableIf = typename std::enable_if<T::value, R>::type;

template<typename T, typename R = void>
using DisableIf = typename std::enable_if<!T::value, R>::type;

template<typename T>
using Unqualified = typename std::remove_reference<typename std::remove_cv<T>::type>::type;

template<typename T>
using Decay = typename std::decay<T>::type;

namespace detail {
// code borrowed from Gears 
// https://github.com/Rapptz/Gears/
template<typename T, typename = void>
struct is_function_impl : std::is_function<typename std::remove_pointer<T>::type> {};

template<typename T>
struct is_function_impl<T, EnableIf<std::is_class<Unqualified<T>>>> {
    using yes = char;
    using no = struct { char s[2]; };

    struct F { void operator()(); };
    struct Derived : T, F { };
    template<typename U, U> struct Check;

    template<typename V>
    static no test(Check<void (F::*)(), &V::operator()>*);

    template<typename>
    static yes test(...);

    static const bool value = sizeof(test<Derived>(0)) == sizeof(yes);
};
} // detail

template<bool B>
using Bool = std::integral_constant<bool, B>;

template<typename T>
struct Function : Bool<detail::is_function_impl<T>::value> {};
} // sol

#endif // SOL_TRAITS_HPP