Re: Opinions about "epsilon" Symbols in Parse Trees

Hi,


"Evangelos Drikos" <drikosv@otenet.gr> said:




> <Identifier> ::= <Identifier start> <Identifier part>
> <Identifier start> ::= <Latin Letter>
> <Identifier part> ::= { <Latin Letter> | <digit> | NONE } .
> /* where NONE is the "epsilon" */
>
> How many times should the Parser reduce the production "<Identifier
> part>-> NONE" when it read an identifier consisting of only one <Latin
> Letter>?


Well, if we assume
A) NONE (Epsilon) is handled like a normal terminal.
    And
B) "{x}" means "zero or more x".


The answer is: infinite times.


What about:


- Treating NONE like a special case (i.e. always an outgoing edge) ?


- Modifying the production, taking NONE out of {}
    <Identifier part> ::= { <Latin Letter> | <digit>
} NONE


- Using a different grammar, for example :
id -> START_CHAR id_part


id_part -> MID_CHAR id_part
                                  | EPSILON


Cheers,
Luigi

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