#pragma once
#include <coroutine>
#include <iterator>
template <typename T>
class Generator {
public:
struct promise_type
{
Generator get_return_object() { return Generator(this); }
std::suspend_never initial_suspend() { return {}; }
std::suspend_always yield_value(T v) // <--- called by co_yield
{
last_value = v; // <--- save yielded value
return {};
}
std::suspend_always final_suspend() noexcept(true) { return {}; }
void return_void() {}
void unhandled_exception() {}
T last_value; // <--- last value co_yield'ed
};
struct sentinel {};
struct iterator
{
std::coroutine_handle<promise_type> coro;
bool operator==(sentinel) const { return coro.done(); }
iterator& operator++()
{
coro.resume();
return *this;
}
T operator*() const
{
return coro.promise().last_value;
}
};
public:
Generator(promise_type* p) : _promise(p) {}
iterator begin() const { return {std::coroutine_handle<promise_type>::from_promise(*_promise)}; }
sentinel end() const { return {}; }
private:
promise_type* _promise;
};
