I have a language in which one expression may immediately follow another. I am
trying to construct an AST with an imaginary node representing the
"concatenation" operator. I want the moral equivalent of
expr: term (SP^ term)*;
except that SP does *not* actually appear in the token stream.
When i try
expr: term (term->(^SP $expr term))*;
i get RewriteEmptyStreamException in that rule on input like
a b c
Here is a tiny grammar that demonstrates the problem:
grammar Test;
options {output=AST;}
prog: expr NL! EOF!;
expr: term (term->^(SP $expr term))*;
term: ID;
fragment
SP : ' '|'\t';
ID : SP*
('a'..'z'|'A'..'Z'|'_'|'\u0080'..'\uFFFE')
('0'..'9'|'a'..'z'|'A'..'Z'|'_'|'\u0080'..'\uFFFE')*
;
NL : ('\r'|'\n')+;
I would appreciate anyone pointing out what i am doing wrong.
--
Trevor John Thompson net: ti...@mac.com
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