{

using sender_concept = stdexec::sender_tag;

using completion_signatures =

stdexec::completion_signatures<stdexec::set_value_t(int),

stdexec::set_error_t(std::exception_ptr)>;

template <class R>

struct op

{

R r_;

void start() & noexcept

{

static int i = 0;

if (++i < 3)

{

std::printf("fail!\n");

stdexec::set_error(std::move(r_), std::exception_ptr{});

}

else

{

std::printf("success!\n");

stdexec::set_value(std::move(r_), 42);

}

}

};

template <class R>

auto connect(R r) const -> op<R>

{

return {std::move(r)};

}

{

auto x = retry(fail_some{});

// prints:

// fail!

// fail!

// success!

auto [a] = stdexec::sync_wait(std::move(x)).value();

(void) a;