有限状态机(Finite automaton) A finite automaton M is a5--tuple(2,qo,A,∑，8)， where O is a finite set of states, ·qo∈O is the start state, .A CO is a distinguished set of accepting states, ·∑is a finite input alphabet, 。8 is a function from O×∑into O,called the transition function of M. input (语句)：=（前缀）a state a b (前缀)=ε (前缀)：=（前缀）b(前缀)aaK前缀)ab 巴科斯范式(Backus-Naur Form,BNF) https://en.wikipedia.org/wiki/Backus%E2%80%93Naur_form有限状态机（Finite automaton） 语句::=前缀 a 前缀::= 前缀::=前缀b | 前缀aa|前缀ab 巴科斯范式(Backus-Naur Form，BNF) https://en.wikipedia.org/wiki/Backus%E2%80%93Naur_form