P.S. I leaned much from Andrew W. Appel, the chapter 3 of "Modern Compiler Implementation in ML"
2012/1/5 Shinji KOBAYASHI <skoba at moss.gr.jp>: > Hi Seref, > > Left recursive rule is theoretically rewrite to equivalent right recursive. > In ADL grammar, cADL has left recursive rule that cannot be parsed by LL, > so I converted them to right recursive rules. > For example of left recursive to explain(shorten for convenience) > > arithmetic_expression: > ? arithmetic_leaf > | arithmetic_node > > arithmetic_node: > ?arithmetic_expression '+' arithmetic_leaf > |... > > arithmetic_leaf: > ?(an arithmetic element) > > I converted this grammar to this right recursive rule. > > arithmetic_expression: > ? arithmetic_leaf > | arithmetic_node > > arithmetic_node: > ?arithmetic_leaf ?'+' arithmetic_expression > |... > > These conversions were the most tough points. > I wish I could help you. > > Regards, > Shinji > > 2012/1/5 Seref Arikan <serefarikan at kurumsalteknoloji.com>: >> Thanks Shinji, >> In general, Antlr has some convenient features, infinite lookahead being one >> of them. I've quickly checked, and Treetop does not seem to support left >> recursion either. So you must have modified the grammar to make it work. >> I'm referring to grammar rules such as >> A : A | B; >> >> Tom made the point earlier. At one point it would be good to unify various >> AQL implementation experiences. I'll check out the papers. >> >> Best regards >> Seref >> >> >> >> On Thu, Jan 5, 2012 at 2:21 AM, Shinji KOBAYASHI <skoba at moss.gr.jp> wrote: >>> >>> Hi Seref, >>> >>> My ADL parser does not include AQL parsing. >>> I used Treetop, which is an Ruby implementation of PEG/Packrat parsing >>> algorithm, >>> not LL/LR. PEG/Packrat parser algorithm was described in this paper. >>> http://bford.info/pub/lang/packrat-icfp02/ >>> >>> Antlr is an implementation of PEG parser by LL techniques. I do not >>> know Antlr so much. >>> >>> Packrat parser does not need to separate scanner/parser/lexer and is >>> capable to >>> infinite look ahead recursive. >>> >>> I do not know why are you parsing AQL, but this proceeding about querying >>> EHR >>> by archetype might be helpful for your research. >>> http://web-ext.u-aizu.ac.jp/labs/sw-db/7108/71080109.pdf >>> >>> Best regards, >>> Shinji >>> >>> 2012/1/5 Seref Arikan <serefarikan at kurumsalteknoloji.com>: >>> > Greetings, >>> > The AQL grammar from the wiki has direct and indirect left recursion. >>> > Which >>> > means without changes in the grammar, LL parser generators (both JavaCC >>> > and >>> > Anltr) can't generate parsers for this grammar. >>> > >>> > I'm curious if anybody has refactored this grammar for LL parser >>> > generators. >>> > Shinji? Your latest release includes an AQL parser does not it? Could >>> > you >>> > please share your method? I can always look at the code, but you'd >>> > probably >>> > save me time :) >>> > >>> > I'm interested in experiences of others too. >>> > >>> > >>> > Kind regards >>> > Seref >>> > >>> > >>> > _______________________________________________ >>> > openEHR-technical mailing list >>> > openEHR-technical at openehr.org >>> > http://lists.chime.ucl.ac.uk/mailman/listinfo/openehr-technical >>> > >>> _______________________________________________ >>> openEHR-technical mailing list >>> openEHR-technical at openehr.org >>> http://lists.chime.ucl.ac.uk/mailman/listinfo/openehr-technical >> >> >> >> _______________________________________________ >> openEHR-technical mailing list >> openEHR-technical at openehr.org >> http://lists.chime.ucl.ac.uk/mailman/listinfo/openehr-technical >>
