Re: Preceding action

[Hans Åberg]

[Please keep the cc to the list so that others can follow.]

> On 13 Nov 2017, at 13:39, Péter <address@hidden> wrote:
> 
> 
> Could not it happen that for bison some input seems first as "A", then later 
> becomes clear that it is not quite "A" but "B"? And by that time (realizing 
> that it is "B") bison have already played some of the actions related to 
> "A"..?
> 
> For example, in the case of our list, we already appended (by mistake) some 
> items to the list..
> 
> (I have noticed "%glr-parser" which is an advanced bison directive but I am 
> not using it sofar and do not intend to.)

If the grammar is unambiguous relative to the parser algorithm, by default 
LALR(1), then the grammar rules are treated as a set and the correct ones to 
apply are computed. If there is an ambiguity, Bison chooses the one first in 
the grammar; if one wants to sort that out, one might try the GLR parser.