On Sunday 27 February 2011 09:00:03 slug-requ...@slug.org.au wrote: > > Sections : > > | Section Sections > > | Lines > > The problem is two-fold. First, it is the convention to write iteration > left recursively, as in > > Sections > : /* empty */ > | Sections Section > ; > > This results in less depth in the parse stack, and in some cases (where > rules are attached) results in a more-expected side-effect order (L2R > rather than R2L). > > The second problem is that both Lines and Sections can be empty. > This make the initial parse state ambiguous. Should it immediately > reduce by the "Sections: /* empty */" rule, or by the "Lines: /* empty > */" rule? > > Try this instead > > Sections > : Lines > | Sections section > ; > > Now there is no empty Sections rule, and all ambiguity goes away... the > file always starts with a (possibly empty) non-section set of lines. > > When it doubt, always read the y.output file, it will document how and > where ambiguities occur in your grammar.
Peter thank you. In a moment you have solved many days of muddling. I *do* read y.output but I'm not clever enough to turn the reported conflict into a solution <blush> James -- SLUG - Sydney Linux User's Group Mailing List - http://slug.org.au/ Subscription info and FAQs: http://slug.org.au/faq/mailinglists.html
