Re: [Flex-help] How to scan for token with no predefined value?

[J. L. T. <jl...@ce...>]

On Wednesday 27 May 2009 01:39:41 Virgil Palanciuc wrote:
>    Hi,
>  So, if I get it straight, your lexer should be something like this:
>
> <INITIAL>{command}     { BEGIN(OPTIONAL_DELIMITER); /* do something for the
> command */  }
> <OPTIONAL_DELIMITER>{whitespace}  { /* do nothing */ }
> <OPTIONAL_DELIMITER>.   {  // I'm using '.', assuming that the delimiter
> must be a single char; you can replace it with any other rule
>                   BEGIN(MORE_SPECIFICATIONS); // delimiter is optional, so
> we enter "MORE_SPECIFICATIONS" state regardless on whether this is indeed a
> delimiter char
>                   if( !isUserDelimiter(yytext) ) yyless(0);  // if the char
> is not delimiter, then don't consume it
>                   else return TOK_DELIMITER;              // if it is a
> delimiter, return the appropriate token to the parser.
> }
>
> <MORE_SPECIFICATIONS>{something}  { /*.....*/; BEGIN(INITIAL) }
>
>    Does this help/did I understand correctly what you are trying to do?
>       Virgil.
>
Virgil,

	Something like that is what I'm looking for.  The switch to 
<OPTIONAL_DELIMITER> can be triggered when the endchar keyword is recognized, 
so it would look something like

<INITIAL>"endchar"                                  {BEGIN(OPTIONAL_DELIMITER)
<OPTIONAL_DELIMITER>[^[[:ALPHANUM:]]]        // tell the parser to save this 
value as endchar

	How do I tell the parser to associate the value with the token for endchar?

Leslie

> On Wed, May 27, 2009 at 7:40 AM, J. L. Turriff <jl...@ce...> wrote:
> >        I'm setting up flex definitions for a scripting language, and I've
> > come
> > across an issue that is not addressed in the flex manual.  The language
> > definition allows the user to define the value of an optional delimiter
> > token
> > at execution-time; the token has no default value.  How do I handle this
> > in the flex definitions?
> >
> >        Here's an example of the usage:
> >
> >                command (endchar ?) more specifications...
> >
> >        The value of endchar has no default (its use is optional in /more
> > specifications/) but whatever value is supplied by the user (in this
> > case "?") must be recognized by the scanner.
> >
> > Leslie
> >
> >
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