Solved! (Re: Yacc probs w/ANSI-C)

Robert Steven Glickstein bobg+ at andrew.cmu.edu
Sat Jun 24 02:56:10 AEST 1989


In: 21-Jun-89 Yacc probs w/ANSI-C, I wrote

> I've written a parser for ANSI-C using YACC (adhering strictly to the
> grammar given in K&R, second edition) that doesn't work.  Despite the
> claim in section A13 that "this grammar is acceptable to the YACC
> parser-generator"(modulo some changes, which I've made), it in fact is
not; it's not even LR(1).

My profuse apologies to Messrs. Kernighan and Ritchie.  I had failed to
follow the advice given in section A13 that tells the Yacc user to write
all rules containing optional subrules twice.  That is to say, I had
written

    foo: bar opt_baz bletch
        ;
    opt_baz:
        | baz
        ;

when I should have written

    foo: bar bletch
        | bar baz bletch
        ;

Converting everything to the latter form fixed my problems.  Thanks to
everyone who responded!


	Bob Glickstein



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