Hello People, being an ANTLR beginner, I would very much appreciate advice concerning good practise for a rather simple task. The task is the translation of a JPQL's (Java Persistence Query Language) "where clause" into a proprietary query language. The clause has the well-known expression structure: operands conncected by three operators: OR, AND and NOT, where precedence increases in that order. Example: a.x='1' AND (a.y='2' OR b.z='3') AND a.v like 'abc%'
An important point is that the translation result will have a similar structure, that is, it will also be operands connected by those operators. Example: x='1' AND (y='2' OR z='3') AND v='123*' For this reason I am not sure if the "classical" approach for dealing with left-associative operators, as shown in the "Definitve ANTLR Reference" (3. A quick tour...) is the most appropriate one in this case. I mean rules like: conditional_term ('OR'^ conditional_term)* conditional_factor ('AND'^ conditional_factor)* This creates deep trees, where each operator creates a new level. That is fine for processing the operations. But a straightforward translation of the tree into a similar sequence of operands and operators yields a result which is correct but can be ugly, due to superflous brackets, example: (a OR (b OR (c AND d))) One possibility is to process the tree, removing superfluous brackets - perhaps by passing the "context operator" into the rule as a parameter, so that the rule can decide if to create brackets or not. This should not be too difficult, but my question is: is there a good practise for accomplishing the task? Would you recommend the approach just sketched, or a different tree representation to start with? (A tree I do want because there are other parts to be translated, not only the where clause, and a tree seems to me the way to deal with (possibly yet growing) complexity. Thank you very much for any suggestions. -- Hans-Juergen 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 il-antlr-inter...@googlegroups.com. To unsubscribe from this group, send email to il-antlr-interest+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/il-antlr-interest?hl=en.