trivial rule does not reduce in ML-Yacc

Hello,


                My problem surely has an easy solution, but I cannot see it.
I'm trying to write a parser, and encountered to an error, what I
reproduced in a very simple example. In ML-Yacc, the START symbol (the
sentence symbol) cannot appear on the right hand side of a rule. So, I
introduced EXPR, what I expected to reduce to START
straightforward. But it does not work this way. What did I wrong?


                                                                - Gergely


I've got:


1 rule not reduced


warning: rule <START : EXPR > will never be reduced
----------
trivi.grm:
----------
%%
%name Trivi
%term NUMBER of string | PLUS | EOF
%nonterm START of string | EXPR of string
%pos int
%verbose
%noshift EOF
%%
START : EXPR (EXPR)


EXPR : EXPR PLUS NUMBER (EXPR ^ "PLUS" ^ NUMBER)
                | NUMBER (NUMBER)


---------------
trivi.grm.desc:
---------------
1 rule not reduced


warning: rule <START : EXPR > will never be reduced


state 0:


                START : . EXPR


                NUMBER shift 2


                START goto 5
                EXPR goto 1


                . error




state 1:


                START : EXPR . (reduce by rule 0)
                EXPR : EXPR . PLUS NUMBER


                PLUS shift 3




                . error




state 2:


                EXPR : NUMBER . (reduce by rule 2)






                . reduce by rule 2




state 3:


                EXPR : EXPR PLUS . NUMBER


                NUMBER shift 4




                . error




state 4:


                EXPR : EXPR PLUS NUMBER . (reduce by rule 1)






                . reduce by rule 1




state 5:








                . error


3 of 9 action table entries left after compaction
2 goto table entries
--

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