Third Lecture (compiler theory) lexical analysis

Regular Expressions

1. Priority of: * (the Kleene closure) connected, | (or operation).

Regular defined

Finite Automata

• With input
• Read head
• Finite Controller

1. FM definition language
2. Longest substring matching principle
   

There are classification of finite automata

1. DFA: deterministic finite automata
2. NFA: non-deterministic finite automata
   
3. Automatic machine with a "E- edge" with automatic machines without "E- edge" having equivalence

• Automatic machine with a "E- edge" is more intuitive
  

DFA implementation

1. DFA can transition diagram or the conversion table indicates
   

Lexical analyzer

RE (regular expressions) - NFA - DFA

From RE to NFA

From NFA to DFA

Subset construction method

Lexical analyzer