[antlr-interest] Re: How to throw an exception from the lexer to the caller rule

[Terence Parr]

On Monday, October 29, 2001, at 01:35  AM, lemoine at multimania.com wrote:

> You're wright.
> The exception was not generated by the lexer rule.
> It's generated by the parser in the uri grammar rule
> (NoViableAltException).
> ...
> But that's not what I want to do. I want to handle my own exception
> for the command in the command rule and for queries in the
> queries rule.

Just specify what to match in the error case (i.e., as regular rule 
stuff) and then have an action that throws the exception...

I see no need for the special uri rule below, by the way...

Terence

>
> The only way I found is to check for two tokens and to replace the
> rule
>
> uri     : command
>         | queries
>
> by the rule
>
> uri             :
>                  {
>                    // it's a query option
>                    if(LT(2).getText().equals("=")) {
>                         queries() ;
>                    } else {
>                    // it's a command
>                         command() ;
>                    }
>                  }
>                 ;
>
> command         : s:STATS
>                   { _commandName = s.getText() ; }
>                 | d:DSINFOS
>                   { _commandName = d.getText() ; }
>                 | p:PINFOS
>                   { _commandName = p.getText() ; }
>                 | h:HELP
>                   { _commandName = h.getText() ; }
>                 {
>                     _requestIsQuery = false ;
>
>                     System.out.println("command is "+_commandName) ;
>                 }
>                 ;
>                 exception // for command
>                 catch [RecognitionException  e] {
>                  String token = getToken(e.getMessage()) ;
>                  throw new RecognitionException("Unknown
> command"+" "+token);
>                 }
>
> queries         : query (SEMI query)*
>                 ;
>                 exception // for queries
>                 catch [RecognitionException  e] {
>                  String token = getToken(e.getMessage()) ;
>                  throw new RecognitionException("Unknown
> option"+" "+token);
>                 }
>
> I don't known if this solution is very clean ... but it works.
> If you have a another way, it would be greatly apprecied.
>
> Thanks
>
> Hervé
>
>
>
> --- In antlr-interest at y..., Terence Parr <parrt at j...> wrote:
>>
>> On Wednesday, October 17, 2001, at 05:46  AM, lemoine at m...
>> wrote:
>>
>>> Hi,
>>> I had specified the testLiterals option to true for the IDENT
> rule in
>>> the Lexer to test each token against the literals table.
>>> But when the literal does not match with the lexer IDENT rule, it
>>> generates an Exception and exits of the lexer.
>>> I want to catch the exception in the caller rule of the parser to
>>> specify my own error message.
>>
>> It should not be generating an exception if it's not a literal...it
>> should simply return as IDENT.  Are you sure that is what is
> happening?
>>
>> Ter
--
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Creator, ANTLR Parser Generator: http://www.antlr.org
>
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