一级理论和二级理论的区别

I hope those who can rate this book will give this book a five-star rating, or at least turn the three stars into four. Those who leave negative reviews will be merciful. After all, writing a book is not easy, and writing Erlang requires more effort than my other books. It's more tiring, and I also have to support my family, so I don't dare to be too hasty....