Regex and BNF

Regex and BNF

1. Regular language

   • Any language an FSM will accept

2. Regex- regular expression

   • A notation for defining all the valid strings of a formal language
     • Formal language
       • Defined using its alphabet and rules of syntax
     • a matches a string of just "a"
       • ab just allows "ab"
       • a* allows 0 or more a's
       • a+ allows 1 or more a's
       • abb? character before ? is optional
       • a|b allows a OR b

3. BNF- Backus-Naur Form

   • A notation for expressing the rules for constructing valid strings in a regular expression