Function do_for_each

demo_example/ReadFiles.cpp:67–81

// It is not travial to implement an asynchronous do_for_each.
template <typename InputIt, typename Callable>
Future<void> do_for_each(InputIt Begin, InputIt End, Callable func) {
    for (auto It = Begin; It != End; ++It) {
        auto F = std::invoke(func, *It);
        // If we met an error, return early.
        if (F.result().hasError())
            return F;
        if (F.hasResult())
            continue;
        return std::move(F).thenTry(
            [SubBegin = ++It, SubEnd = End, func](auto &&) {
                return do_for_each(SubBegin, SubEnd, func);
            });
    }
    return makeReadyFuture();
}

template <Range RangeTy, typename Callable>
Future<void> do_for_each(const RangeTy &Rng, Callable func) {