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Parser rule to allow apostrophe and quotes [message #687625]

Wed, 22 June 2011 21:37

Chetan Kumar

Messages: 44
Registered: July 2009

Member

folks,

i have a keyword in my dsl which is like so:

@description <value>

Value can be anything - one line description, multi-line description, with lot of characters used (' , " * : ^). The value is not enclosed in quotes (" | '). More importantly, value can have ' character as many number of times as possible.

I tried these set of rules:

ZDESCRIPTION : (ID(ZSYMBOL)*)+;

// allowed symbols
ZSYMBOL : ('"'|"'"|"'"|'<'|'/'|'>'|'\\'|','|'^'|'-'|'+'|'.'|':'|'*'|INT|'['|']');

while generating code i get these warnings: Decision can match input such as "'\''" using multiple alternatives: 2, 3As a result, alternative(s) 3 were disabled for that input.

I even tried "\\'" in ZSYMBOL but result is the same. Generated editor shows an error marker for something like this:

@description simple description copied from Pete's tag.

How to allow apostrophes in values ?

+ Chetan

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Re: Parser rule to allow apostrophe and quotes [message #687665 is a reply to message #687625]

Thu, 23 June 2011 00:15

Henrik Lindberg

Messages: 2509
Registered: July 2009

Senior Member

You are probably using a terminal that eats the apostrophe (the String
terminal).

If your description ends with something distinct (or end of line), it is
probably ok with just a new terminal rule that eats until end of line.

The best is probably to solve this at the lexer level using an external
lexer as you need rules that allows unbalanced ' and ".

Regards
- henrik

On 6/22/11 11:37 PM, Chetan Kumar wrote:
> folks,
>
> i have a keyword in my dsl which is like so:
> @description <value>Value can be anything - one line description,
> multi-line description, with lot of characters used (' , " * : ^). The
> value is not enclosed in quotes (" | '). More importantly, value can
> have ' character as many number of times as possible.
>
> I tried these set of rules:
> ZDESCRIPTION : (ID(ZSYMBOL)*)+;
>
> // allowed symbols
> ZSYMBOL :
> ('"'|"'"|"'"|'<'|'/'|'>'|'\\'|','|'^'|'-'|'+'|'.'|':'|'*'|INT|'['|']');
>
> while generating code i get these warnings: Decision can match input
> such as "'\''" using multiple alternatives: 2, 3As a result,
> alternative(s) 3 were disabled for that input.
>
> I even tried "\\'" in ZSYMBOL but result is the same. Generated editor
> shows an error marker for something like this:
> @description simple description copied from Pete's tag. How to allow
> apostrophes in values ?
>
> + Chetan
>

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Re: Parser rule to allow apostrophe and quotes [message #689345 is a reply to message #687665]

Mon, 27 June 2011 13:37

Chetan Kumar

Messages: 44
Registered: July 2009

Member

thanks Henrik.

I think an 'until' rule will be the best fit for '@description'. However, there is no definite end for '@description' keyword. The start of the next '@<keyword>' is where '@description' ends. But if I define a terminal rule to consume everything until next '@' that will include '@' as part of '@description'.

+ Chetan

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