Example Identifiers like: A1BC_3A_B5 Identifier cannot end in an underscore It cannot contain two consecutive underscores Solution: Divide.

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Presentation transcript:

Example Identifiers like: A1BC_3A_B5 Identifier cannot end in an underscore It cannot contain two consecutive underscores Solution: Divide the identifier into three parts A 1BC _3A_B5 L (L|D)* (_(L|D)+)*

RE: / * (not *)* ( *+ (not /) (not *)* )* *+ /

Implementation Issues Handling reserved words Implementing finite automaton Input buffering

Implementing Finite Automaton Table Driven Index into a table using <state#, input ASCII code> Table entry gives the next state Use negative entries to signal actions like errors