Ref:
https://blog.csdn.net/qq_35208390/article/details/78249181
flex and bison: https://www.cnblogs.com/lyr2015/p/6099687.html
有窮自動機(狀態機):https://blog.csdn.net/qq_39521554/article/details/79416553
移進-規約算法:https://wenku.baidu.com/view/000f954df111f18582d05a35.html