Thank you very much. Saved now.
On Fri, Mar 6, 2015 at 5:10 PM, Jeffrey Kegler <jeffreykeg...@jeffreykegler.com> wrote: > Andreas: Your example is in this Github gist: > https://gist.github.com/jeffreykegler/1dd56ce50c1dd2395856 > > On Fri, Mar 6, 2015 at 2:44 PM, Andreas Kupries > <andre...@activestate.com> wrote: >> That should really help with understanding this. Thanks. >> >> On Fri, Mar 6, 2015 at 2:38 PM, Jeffrey Kegler >> <jeffreykeg...@jeffreykegler.com> wrote: >>> Andreas: Actually, it occurs to me that I can work up an example from >>> Marpa's internal trace mechanisms, showing the internal rules. I'm >>> away from my development environment now, but I'll do that in a bit. >>> >>> On Fri, Mar 6, 2015 at 12:30 PM, Andreas Kupries >>> <andre...@activestate.com> wrote: >>>> On Fri, Mar 6, 2015 at 12:08 PM, Jeffrey Kegler >>>> <jeffreykeg...@jeffreykegler.com> wrote: >>>>> No. Sorry if I was not clear. >>>> >>>> No problem. >>>> >>>>> >>>>> The rewrite for precedenced rules removes the ambiguity of the pure >>>>> BNF in the SLIF DSL, and in this way is very much like the one you see >>>>> described elsewhere, particularly for dealing with expressions using >>>>> top-down parsers. You add a new symbol for the expression at each >>>>> level of precedence, and the rewritten BNF will be unambiguous. >>>> >>>> Ok. Guess I have to google then for bnf rewriting. >>>> Thanks for your time. >>>> >>>>> >>>>> On Fri, Mar 6, 2015 at 11:50 AM, Andreas Kupries >>>>> <andre...@activestate.com> wrote: >>>>>> On Fri, Mar 6, 2015 at 11:33 AM, Jeffrey Kegler >>>>>> <jeffreykeg...@jeffreykegler.com> wrote: >>>>>>> For the precedenced rules, you create new symbols for each precedence, >>>>>>> proceeding with associativity in the obvious way. Much of it is done >>>>>>> in this routine: >>>>>>> https://github.com/jeffreykegler/Marpa--R2/blob/master/cpan/lib/Marpa/R2/MetaAST.pm#L568 >>>>>> >>>>>> Thank you. >>>>>> It reminds me that I have not read perl code since Perl4. >>>>>> I believe it will take me a while to decipher that. >>>>>> >>>>>>> One thing to note is that it is *not* operator precedence -- the rule >>>>>>> have precedence, and the operators play no special role. >>>>>> >>>>>> So, in essence the rewrite generates an ambiguous grammar which the >>>>>> engine has no problems with, parsing them all in parallel, right ? >>>>>> >>>>>> And at the end the rule priorities are then used to collapse >>>>>> ambiguity, by keeping only the highest priority at each node ?! >>>>>> >>>>>> And I further guess that the only ambiguities which survive to the >>>>>> parse forest are those which have the same highest priority at a node. >>>>>> >>>>>>> It's not dissimilar to rewrites you'll see elsewhere, but I might be >>>>>>> its inventor, if only because nobody previously had a parser that >>>>>>> could be expected to parse the rewritten rules. >>>>>>> >>>>>>> On Fri, Mar 6, 2015 at 11:22 AM, Andreas Kupries >>>>>>> <andreas.kupr...@gmail.com> wrote: >>>>>>>> >>>>>>>> >>>>>>>> On Thu, Mar 5, 2015 at 4:51 PM, Jeffrey Kegler >>>>>>>> <jeffreykeg...@jeffreykegler.com> wrote: >>>>>>>>> >>>>>>>>> Quantified rules are semantic sugar for BNF, and you can write BNF >>>>>>>>> rules >>>>>>>>> and have access to all the symbols in them, including those you think >>>>>>>>> of as >>>>>>>>> separators. I say "think of", because if separators are given a >>>>>>>>> semantics, >>>>>>>>> they are (conceptually) more than just separators. Sequences can be >>>>>>>>> written >>>>>>>>> as recursions -- internally, that is what Marpa::R2 actually does. >>>>>>>> >>>>>>>> >>>>>>>> Is there any documentation around on how Marpa::R2 rewrites the sugar >>>>>>>> into >>>>>>>> basic BNF ? >>>>>>>> >>>>>>>> Ok, I know how it can be done for the quantified rules, via left >>>>>>>> recursion >>>>>>>> and additional non-terminals. However for the priority rules I am >>>>>>>> still not >>>>>>>> fully clear how these would be done. >>>>>>>> >>>>>>>> If there is no documentation, then is the rewrite engine in some >>>>>>>> central/singular place in the sources, or is its activity distributed >>>>>>>> through it, and where would I have to look ? >>>>>> >>>>>> >>>>>> >>>>>> -- >>>>>> Andreas Kupries >>>>>> Senior Tcl Developer >>>>>> Code to Cloud: Smarter, Safer, Faster™ >>>>>> F: 778.786.1133 >>>>>> andre...@activestate.com, http://www.activestate.com >>>>>> Learn about Stackato for Private PaaS: >>>>>> http://www.activestate.com/stackato >>>>>> >>>>>> -- >>>>>> You received this message because you are subscribed to the Google >>>>>> Groups "marpa parser" group. >>>>>> To unsubscribe from this group and stop receiving emails from it, send >>>>>> an email to marpa-parser+unsubscr...@googlegroups.com. >>>>>> For more options, visit https://groups.google.com/d/optout. >>>>> >>>>> -- >>>>> You received this message because you are subscribed to the Google Groups >>>>> "marpa parser" group. >>>>> To unsubscribe from this group and stop receiving emails from it, send an >>>>> email to marpa-parser+unsubscr...@googlegroups.com. >>>>> For more options, visit https://groups.google.com/d/optout. >>>> >>>> >>>> >>>> -- >>>> Andreas Kupries >>>> Senior Tcl Developer >>>> Code to Cloud: Smarter, Safer, Faster™ >>>> F: 778.786.1133 >>>> andre...@activestate.com, http://www.activestate.com >>>> Learn about Stackato for Private PaaS: http://www.activestate.com/stackato >>>> >>>> -- >>>> You received this message because you are subscribed to the Google Groups >>>> "marpa parser" group. >>>> To unsubscribe from this group and stop receiving emails from it, send an >>>> email to marpa-parser+unsubscr...@googlegroups.com. >>>> For more options, visit https://groups.google.com/d/optout. >>> >>> -- >>> You received this message because you are subscribed to the Google Groups >>> "marpa parser" group. >>> To unsubscribe from this group and stop receiving emails from it, send an >>> email to marpa-parser+unsubscr...@googlegroups.com. >>> For more options, visit https://groups.google.com/d/optout. >> >> >> >> -- >> Andreas Kupries >> Senior Tcl Developer >> Code to Cloud: Smarter, Safer, Faster™ >> F: 778.786.1133 >> andre...@activestate.com, http://www.activestate.com >> Learn about Stackato for Private PaaS: http://www.activestate.com/stackato >> >> -- >> You received this message because you are subscribed to the Google Groups >> "marpa parser" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to marpa-parser+unsubscr...@googlegroups.com. >> For more options, visit https://groups.google.com/d/optout. > > -- > You received this message because you are subscribed to the Google Groups > "marpa parser" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to marpa-parser+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. -- Andreas Kupries Senior Tcl Developer Code to Cloud: Smarter, Safer, Faster™ F: 778.786.1133 andre...@activestate.com, http://www.activestate.com Learn about Stackato for Private PaaS: http://www.activestate.com/stackato -- You received this message because you are subscribed to the Google Groups "marpa parser" group. 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