Thanks, Jim. Please understand though that I dumbed down the test
grammar to minimally illustrate the problem I was asking about - my
actual grammar shapes a much more complex tree and uses "tidy
tokens";). The revision you suggest unfortunately looses a bit too much
intrinsic information that would be difficult to infer if at all in a
later pass. As I mentioned, the order, existence and position of the
parens and leading dots are significant - (foo), .foo, (.foo), and foo
are not equivalent and need to be distinctly represented in the tree.
On 3/19/2010 10:41 AM, Jim Idle wrote:
> That will give a tree that isn't very useful ;-) You need to express this in
> LL form such that the things that can be elements of your compound appear at
> the bottom of the tree. Then use DOT and not '.', make that be the root node
> and do not try to impose any semantic verification via syntactical
> specifications. You get:
>
>
> grammar T;
>
> options { output=AST; }
>
> tokens { EXPR; FUNC;}
>
> aago : (expr NL)+ EOF
> ->^(EXPR expr)+
> ;
>
> expr
> : element (DOT^ element)*
> ;
>
> element
> : LPAREN! expr RPAREN! // Sometimes you want to preserve the LPAREN
> here
> | ID (LPAREN^ expr RPAREN)? // function call
> ;
>
> LPAREN : '(' ;
> RPAREN : ')' ;
> ID : ('A'..'Z')+ ;
> DOT : '.' ;
> NL : ('\n'|'\r')+ ;
> ANY : . {skip();} ;
>
>
>
>> -----Original Message-----
>> From: [email protected] [mailto:antlr-interest-
>> [email protected]] On Behalf Of Gerald Rosenberg
>> Sent: Friday, March 19, 2010 10:01 AM
>> To: antlr-interest interest
>> Subject: [antlr-interest] Problem removing warning
>>
>> Having a bit of difficulty in figuring out how to unambiguously parse
>> this into an AST.
>> Order of the elements is significant, the parens are significant, and
>> the leading dot is significant.
>>
>> (.buf_unittest.complex_opt1).foo;
>> .buf_unittest.complex_opt1.fum;
>> (buf_unittest.complex_opt1).(.buf_unittest.quux);
>> (.buf_unittest.complex_opt1).(buf_unittest.corge).qux;
>> (complex_opt2).baz;
>> (complex_opt2).(grault);
>> (complex_opt2).bar.foo;
>> (complex_opt2).bar.(quux);
>> (complex_opt2).bar.(buf_unittest.corge).qux;
>> (complex_opt2).(garply).foo;
>> (complex_opt2).(garply).(.buf_unittest.quux);
>> (complex_opt2).(buf_unittest.garply).(corge).qux;
>> (ComplexOptionType2.ComplexOptionType4.complex_opt4).waldo;
>> (complex_opt2).fred.waldo;
>> (buf_unittest.complex_opt3).qux;
>> (complex_opt3).complexoptiontype5.plugh;
>> (complexopt6).xyzzy;
>>
>> The rule ident_parens following appears to work, but Antlr is
>> complaining "Decision can match input such as "'.' ID" using multiple
>> alternatives: 1, 2" on both identN and identO. I can see the
>> theoretical overlap, but cannot tell if the warning is actually
>> significant or how to fix the rules to avoid the warning.
>>
>> ident_parens
>> : (identM | identN | identO ) ('.' ( identM | identO ) )*
>> ;
>>
>> identM
>> : '(' '.' ipd+=ID ( '.' ipd+=ID )* ')' -> ^( IDENT_PARENSDOT
>> $ipd+ )
>> | '(' ip+=ID ( '.' ip+=ID )* ')' -> ^( IDENT_PARENS $ip+
>> )
>> ;
>>
>> identN
>> : '.' id+=ID ( '.' id+=ID )* -> ^( IDENT_DOT $id+ )
>> ;
>>
>> identO
>> : i+=ID ( '.' i+=ID )* -> ^( IDENT $i+ )
>> ;
>>
>>
>> Thanks...
>>
>
>
>
>
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