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// This file is part of CAF, the C++ Actor Framework. See the file LICENSE in
// the main distribution directory for license terms and copyright or visit
// https://github.com/actor-framework/actor-framework/blob/master/LICENSE.
#pragma once
#include <string>
#include "caf/detail/comparable.hpp"
namespace caf {
/// Unit is analogous to `void`, but can be safely returned, stored, etc.
/// to enable higher-order abstraction without cluttering code with
/// exceptions for `void` (which can't be stored, for example).
struct unit_t : detail::comparable<unit_t> {
constexpr unit_t() noexcept = default;
constexpr unit_t(const unit_t&) noexcept = default;
constexpr unit_t& operator=(const unit_t&) noexcept = default;
template <class T>
explicit constexpr unit_t(T&&) noexcept {
// nop
}
static constexpr int compare(const unit_t&) noexcept {
return 0;
}
template <class... Ts>
constexpr unit_t operator()(Ts&&...) const noexcept {
return {};
}
};
static constexpr unit_t unit = unit_t{};
/// @relates unit_t
template <class Processor>
void serialize(Processor&, const unit_t&, unsigned int) {
// nop
}
/// @relates unit_t
inline std::string to_string(const unit_t&) {
return "unit";
}
template <class T>
struct lift_void {
using type = T;
};
template <>
struct lift_void<void> {
using type = unit_t;
};
template <class T>
struct unlift_void {
using type = T;
};
template <>
struct unlift_void<unit_t> {
using type = void;
};
} // namespace caf
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