Hello All I'm writing a parser for a fairly simple language (14 rules & 10 tokens) that reads a description of a graph -- like this OncoPrint <http://cbio.mskcc.org/cancergenomics-dataportal/index.do?case_set_id=gbm_3way_complete&tab_index=tab_visualize&action=Submit&genetic_profile_ids=gbm_mutations&genetic_profile_ids=gbm_cna_rae&genetic_profile_ids=gbm_mrna_zscores&case_ids=&Z_SCORE_THRESHOLD=1.0&cancer_type_id=gbm&gene_list=EGFR+ERBB2+PDGFRA+MET+KRAS+NRAS+HRAS+NF1+SPRY2+FOXO1+FOXO3+AKT1+AKT2+AKT3+PIK3R1+PIK3CA+PTEN&gene_set_choice=glioblastoma:_rtk/ras/pi3k/akt_signaling_%2817_genes%29&;> -- of cancer data and produces a data structure that will be used to select, organize and filter the data to be shown in the graph. Users will enter the language on our web site.
I have a working one-pass grammar, but after building it found that it's very difficult to produce error messages in one pass. For example, one might think that a failed semantic predicate would be a good place to report an error, but that doesn't work because exceptions are not thrown when predicates are hoisted and predicates are called multiple times as the parser backtracks to find a parse. (See my previous message on use of semantic predicates and hoisting <http://www.antlr.org/pipermail/antlr-interest/2010-November/040091.html>.) I simply want to say things like "Syntax error at 'xyz' at char <c> on line <l>" // when the input syntax is wrong (I can't say "line 1:0 no viable alternative at input 'xyz'"), and "<input> is not a valid <type> at char <c> on line <l>" // when the input semantics is wrong, for example when <input> should be a word that fits a pattern that describes a genetic data type Therefore, I'm told that one should postpone error reporting until later, and that I need a two pass grammar -- 1) build AST, 2) walk the tree -- to easily and accurately report errors. I've started down that path, and have a few productions in each grammar and a driver program that connects them and handles bits of input. I think that I can report the syntax errors by overriding public void displayRecognitionError(String[] tokenNames, RecognitionException e) and public String getErrorMessage(RecognitionException e, String[] tokenNames) in Phase 1, But it isn't clear how one accesses data in the AST with the tree grammar. That is, inside the tree grammar how do I get the data I need to produce the semantic error message above? Is that documented? I don't see it in The Definitive ANTLR Ref, Chap. 8 or 10. Thanks & Thanksgiving Arthur -- Senior Research Scientist Computational Biology Memorial Sloan-Kettering Cancer Center List: http://www.antlr.org/mailman/listinfo/antlr-interest Unsubscribe: http://www.antlr.org/mailman/options/antlr-interest/your-email-address -- You received this message because you are subscribed to the Google Groups "il-antlr-interest" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/il-antlr-interest?hl=en.
