Re: Getting rid of backups in flex.

It may or may not solve your immediate problem, but you are overdoing
this specification. I would get rid of the tError production
altogether. You can take care of this & all lexical errors with the
parser, with a final rule


.. return yytext[0];


at the bottom of the grammar. This rule also takes care of all single
special characters as well, which is nice: you can get rid of


"+" return '+';
"-" return '-';
";" return ';';
"." return '.';


etc, and use '+' etc literally in the grammar (I'm assuming you're using
yacc).


Esmond Pitt


Robert Minsk wrote:
>
> Given the following rules I am still getting 1 backup I'm trying to
> get rid of.
>
> DIGIT [[:digit:]]
> EXP [Ee][+-]?{DIGIT}+
> EXPERR [Ee][+-]?
> %%
> [-+]?{DIGIT}+ { return tInt; }
>
> [-+]?{DIGIT}*"."{DIGIT}+{EXP}? |
> [-+]?{DIGIT}+"."{DIGIT}*{EXP}? |
> [-+]?{DIGIT}+{EXP} { return tFloat }
>
> [-+]?{DIGIT}*"."{DIGIT}+{EXPERR}? |
> [-+]?{DIGIT}+"."{DIGIT}*{EXPERR}? |
> [-+]?{DIGIT}+{EXPERR}
> . { return tError }
>
> I get:
> State #9 is non-accepting -
> associated rule line numbers:
> 7 11
> out-transitions: [ 0-9 ]
> jam-transitions: EOF [ \000-/ :-\377 ]
>
> 1 backing up (non-accepting) states.

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