[antlr-interest] "throws" clause in v3 Rule Syntax.

Don Maier dMaier at genome.stanford.edu
Thu Jun 14 12:06:46 PDT 2007


Good day,

There has been some discussion of the "throws" clause in ANTLR v3  
dating back to the beginning of April, but I'm not aware of anything  
since.

The documented v3 Rule Syntax (http://www.antlr.org/wiki/display/ 
ANTLR3/ANTLR+v3+printable+documentation) is:

---------------

Rule syntax

/** rule comment */
access-modifier rule-name[«arguments»] returns [«return-values»]  
throws name1, name2, ...
options {...}
scope {...}
scope global-scope-name;
@init {...}
@after {...}
     : «alternative-1» -> «rewrite-rule-1»
     | «alternative-2» -> «rewrite-rule-2»
     ...
     | «alternative-n» -> «rewrite-rule-n»
     ;
     catch [«exception-arg-1»] {...}
     catch [«exception-arg-2»] {...}
     finally {...}

---------------

It appears to me that:

1) ANTLRWorks 1.0.2 disallows the "throws" clause.

2) ANTLR 3.0 ignores it.

3) The syntactic description above may be interpreted to mean that  
the "throws" clause cannot appear without the "returns" clause (and  
conversely).  That does not appear to be correct -- or, at least,  
what we would want.

4) The "throws" clause is *really* important for any *real*  
application of ANTLR:   Is there any other means of returning  
semantic errors found in semantic analysis interspersed with the parse?

Any information about this would be immensely appreciated.

Thank you!

Regards,
Don Maier
Sr. Software Designer/Research
Dept. of Biochemistry
Stanford University School of Medicine


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