[antlr-interest] Tree walker exception handling

[Cameron Esfahani]

I know the questions are a bit open-ended, but does anyone have any  
suggestions?

On May 22, 2007, at 5:25 PM, Cameron Esfahani wrote:

> I'm developing a language that supports assignment:
>
> foo = 125
> bar = foo + 1
>
> Obviously, I need to create a symbol table to hold all of the  
> assignment operations, and then validate all symbols against that  
> table.
>
> From what I can tell, I should be doing this in a tree walker  
> pass.  The problem I'm having is, what do I do when I find a  
> logical versus syntactical error?  For example, when the user  
> erroneously supplies a symbol that doesn't exist?
>
> Right now, I'm just throwing a RecognitionException from within the  
> relevant tree walker rule, and I have a @rulecatch which grabs this:
>
> @rulecatch {
> 	catch ( RecognitionException e ) {
> 		System.exit( 0 );
> 	}
> }
>
> I call System.exit() because I don't want the exception stack frame  
> printing out.  It would scare my users.
>
> In the handler, I want to print out some useful information, like  
> the name and line number of the undefined symbol.  Can I still get  
> this lexer information from a tree walker?
>
> Is it appropriate to use the RecognitionException for these kind of  
> logical errors?  I'm almost wondering if I should create my own  
> class of errors and then throw them as appropriate.
>

Cameron Esfahani
dirty at apple.com

"Americans are very skilled at creating a custom meaning from  
something that's mass-produced."

Ann Powers


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