[antlr-interest] implementing 'if' and 'while' grammar with actions

[向秦贤]

Hi,
If I get you right, I think maybe there is a tree walker needed.
If I do that I would let lexer and parser do thing simply, and create a tree
grammar in which I can  do more thing.




2007/8/24, Abhijit Nandkumar Ghonge <Abhijit_Ghonge at infosys.com>:
>
>  Hi,
>
>
>
> I managed to skip the statements for "if" statement implementation using
> stack concept. Now, I want to implement looping in "while" statement. My
> rule for while statement is:
>
>
>
> whilestatement:
>
>                         'while' LPAREN expr RPAREN 'do' NEWLINE
>
>                         {
>
>                                     //action to push the outcome of expr
> on stack
>
>                         } statement* done
>
>                         {
>
>                                     // peep the top of the stack
>
>                                     // *if expr is true reposition the
> line number of parser to start of while statement*
>
>                                     // else pop the top of the stack and
> continue ahead
>
>                         }
>
>
>
> I'm stuck at the logic to be put for the *bold* comments above. *Is there
> something like yylineno as in yacc parser, which, if I set the line number
> of while statement, it loops back?*
>
> * *
>
> *Please help.*
>
> * *
>
> Regards,
>
> Abhijit.
>
>
>
>
>
>
>  ------------------------------
>
> *From:* antlr-interest-bounces at antlr.org [mailto:
> antlr-interest-bounces at antlr.org] *On Behalf Of *Abhijit Nandkumar Ghonge
> *Sent:* Thursday, August 23, 2007 6:19 PM
> *To:* antlr-interest at antlr.org
> *Subject:* [antlr-interest] implementing 'if' and 'while' grammar with
> actions
> *Importance:* High
>
>
>
> Hi all,
>
>
>
> I want to implement parser grammar for 'if' and 'while' statement *with
> actions in it*.
>
> My script is :
>
>
>
> var1=10
>
> if ( var1 < 9 ) then
>
> var1++
>
> print (var1)
>
> endif
>
>
>
> How do I skip the execution of the statements if the "if-condition" is
> false as in the above case?
>
>
>
> I searched for the grammar implementation in the site, but all examples
> where implementing grammar rules for "if" and "while" without actions in
> them. I want to embed actions in the grammars.
>
> Please give some pointers to "if" or "while" grammar implementation with *actions
> in it.*
>
> Please Help.
>
>
>
> thanks,
>
> Abhijit
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-- 
致敬
向秦贤
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