If all the information is available in y.output then surely modifying yacc will cut out the middle man.
On my list. brucee On 12 November 2011 20:23, Bakul Shah <ba...@bitblocks.com> wrote: > On Fri, 11 Nov 2011 12:54:28 PST Bakul Shah <ba...@bitblocks.com> wrote: >> On Fri, 11 Nov 2011 08:07:21 PST ron minnich <rminn...@gmail.com> wrote: >> > If somebody wants to look at enhancing yacc so that the extra bison >> > bits can be supported, that would probably do the trick. I have no >> > idea of the level of effort, I have not looked. >> >> After some googling I see that src/cmd/gc/bisonerrors was >> added by Russ in an evening to improve go error messages. >> >> Clinton Jeffery in his "Generating LR syntax error messages >> from examples" paper (http://www.cs.nmsu.edu/~jeffery/merr.pdf >> -- not sure if this is the same paper as the one in TOPLAS) >> says his Merr program works with Berkeley yacc, AT&T yacc & >> bison. He also refers to a modified byacc called iyacc. >> >> Might it be worth looking Merr or iyacc? Porting bison to >> plan9 seems like a hugh punishment for a quick hack:-) >> Implementing Jeffery's directly in yacc might benefit other >> parsers as well. > > Reading Merr code was useful but it is written in Icon so.... > > After staring at go.y, bisonerrors, go.errors, bison's > y.output, and generated yerr.h for a while I think I > understand what is going on. I believe everything needed is > already in plan9's y.output -- no need to change yacc. It may > be easier to just make bisonerrors handle this than convert > plan9's y.output to bison compatible y.output. Of course, > things may look much bleaker in the morning but this is what I > think now! > > Given that an array of <state, terminal, message> is generated > from y.output & go.errors, it is may be worth integrating this > logic in yacc. But that is for another day. > > Ideally something like go.errors is interactively generated > from actual errors (sort of like how a spellchecker works -- > you are presented with an error + its context and you indicate > the error message &/or fix). This is then fed back to yacc > along with the grammar. > > -- Don't meddle in the mouth -- MVS (0416935147, +1-513-3BRUCEE)
