[antlr-interest] Specifying limit on number of digits in the Grammar in ANTLR

[Eric Fesh]

I'm currently using V2 until V3 comes out of beta. Does option 3 work with V2?

--

Eric Fesh
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Verari Systems Software, Inc.
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fesh at verarisoft.com
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Alexandre Porcelli wrote:
> This problem is well described in the new Ter book (page 292, in my
> last beta version).
> 
> In fact there is 3 ways to do it:
> 
> 1) Simple context-free grammar
> 
> ID: DIGIT DIGIT DIGIT DIGIT DIGIT
> | DIGIT DIGIT DIGIT DIGIT
> | DIGIT DIGIT DIGIT
> | DIGIT DIGIT
> | DIGIT
> ;
> 
> 2) Verify the size using actions
> 
> ID: ( d+=DIGIT)+ {if ( $d.size() > 5 ) <<error action>> }?
> ;
> 
> 
> 3) Using validating semantic predicate
> 
> ID: ( d+=DIGIT)+ {$d.size() <= 5}?
> ;
> 
> 
> What is the best solution? It always depends (on my point of view) but
> if sometimes you will need to change your grammar to accept 7 instead
> of 5 digits… I would choose the third one.
> 
> Alexandre Porcelli
> 
> 
> On 4/26/07, Bharath R <rbharath24 at yahoo.com> wrote:
>> Hi,
>>
>>       I'm a newbie to ANTLR.
>>         I am trying to write a simple parser, that accepts number whose
>> number of digits vary from 1 to 5.
>>
>>     Below is the ABNF format
>>  ID: 1*5(DIGIT)
>>  DIGIT: '0'..'9'
>>
>>  i.e the ID can be any number varying from a 1 digit number to a max of
>> 5digit number. Each digit varying between 0 and 9.
>>  How do I achieve this in ANTLR? I have been trying to write an 
>> equivalent
>> EBNF format but without success.
>>  Thanks for you help.
>>
>> Regards,
>> Bharath
>>
>>
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