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hyperrogue/hyper_function.h

71 lines
1.9 KiB
C++

#pragma once
#include <type_traits>
#include <utility>
namespace hr {
template<class Sig>
class function;
template<class R, class... Args>
struct function_state_base {
virtual R call(Args...) const = 0;
virtual function_state_base *clone() const = 0;
virtual ~function_state_base() {}
};
template<class T, class R, class... Args>
struct function_state : function_state_base<R, Args...> {
T t_;
explicit function_state(T t) : t_(std::move(t)) {}
R call(Args... args) const override {
return const_cast<T&>(t_)(static_cast<Args&&>(args)...);
}
function_state_base<R, Args...> *clone() const override {
return new function_state(*this);
}
};
template<class R, class... Args>
class function<R(Args...)>
{
function_state_base<R, Args...> *ptr_;
public:
function() : ptr_(nullptr) {}
template<class Callable, class = decltype(R(std::declval<typename std::decay<Callable>::type>()(std::declval<Args>()...)))>
function(Callable&& t) :
ptr_(new function_state<typename std::decay<Callable>::type, R, Args...>(static_cast<Callable&&>(t)))
{}
~function() {
delete ptr_;
}
function(function& rhs) : ptr_(rhs.ptr_ ? rhs.ptr_->clone() : nullptr) {}
function(const function& rhs) : ptr_(rhs.ptr_ ? rhs.ptr_->clone() : nullptr) {}
function(function&& rhs) noexcept : ptr_(rhs.ptr_) { rhs.ptr_ = nullptr; }
function(const function&& rhs) = delete;
void operator=(function rhs) noexcept {
std::swap(ptr_, rhs.ptr_);
}
R operator()(Args... args) const {
return ptr_->call(static_cast<Args&&>(args)...);
}
explicit operator bool() const noexcept {
return ptr_ != nullptr;
}
template<class T> T* target() {
auto ptr = dynamic_cast<function_state<T, R, Args...>*> (ptr_);
if(!ptr) return nullptr;
return &ptr->t_;
}
};
} // namespace hr