Being a new guy at ANTLR... I pretty sure this will take me a while to digest. :)
Thanks, Scott -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Jim Idle Sent: Thursday, January 22, 2009 12:16 PM Cc: [email protected] Subject: Re: [antlr-interest] Tree Evaluation with Logical Operators (AND and OR) > > 2009/1/22 Priolo, Scott <[email protected]>: > >> Sorry about that, I'm trying to setup a walker that will know what to do >> with "OR" and "AND" operators. I have the parser setup so that the AST is >> nicely formed with expr such as (< a 3). I'm able to walk and evaluate >> these simple expr too. But! when I walk (or (and (< a 3) (< b 3)) (< c 3)) >> I'm stumped. >> You need to make your rules within an expression return a type, the formulation of which depends on what things you can evaluate. If your primitive types are all integer, then each stage of your expression can return integer and the AND and OR rules can return 0 and 1. Otherwise, you will need to create a class with 'operators' such as plus(), minus(), and() etc. It will also contain an integer, perhaps a boolean, perhaps a String and so on. Before applying your operations, you will need to coerce the types according to some orthogonal rules, as in if you have ^(AND INT STRING), what does that mean to you - do you convert the string to an integer, or does it mean "is not null" for instance, and what do want to do with ^(AND INT STRING) vs ^(AND STRING INT) (promotion rules, diamonds and so on). If it is just Integer though, then: if: ^(IF e=expr ....) { if ($e.intVal != 0) { .... expr returns [int intVal] : : i=INT { intVal = stringtoint($i.text); ... some conversion func : ^(AND e1=expr e2=expr) { if (stringtoint($e1.text) !=0 && stringtoint($e2.text) != 0) { intVal = 1; }.... .... and so on. Jim List: http://www.antlr.org/mailman/listinfo/antlr-interest Unsubscribe: http://www.antlr.org/mailman/options/antlr-interest/your-email-address 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 -~----------~----~----~----~------~----~------~--~---
