Re: avoiding infinite loops

[David Russinoff]

>It's not much, but I think it is a little clearer at least.  Here's how 
>mine looks:
>
>state 2
>
>    0 $accept: p . $end
>    3 a: p .  [$end]
>
>    $end  shift, and go to state 4
>
>    $end  [reduce using rule 3 (a)]
>
>As Hans said, the shift (for the Bison-generated rule 0) is chosen, and so 
>the reduce (rule 3 with lookahead) can't even be encoded in the LALR(1) 
>action table.  The reduce is printed above just to show the conflict.
>
>Joel

It would appear that my Bison has a bug, not in the parser generator itself,
but in the generation of the "output" file.  The output above is more suggestive
of the observed bahavior than the output that I get.

The line

>    3 a: p .  [$end]

is the interesting one.  I suppose it's saying that the rule should not be 
reduced
unless the lookahead token is $end.  This must be what you mean by "lookahead
information".  I do not understand how Bison derives this information.  Can 
anyone
explain this aspect of the algorithm or tell me how I can learn about it?