[antlr-interest] expression parser example Expr.g dont work

[Mats Ekberg]

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7 jan 2009 kl. 19.40 skrev "Jack Pan" <Jack.Pan at Lewtan.com>:

> How does AntlrWorks pick the default starting rule? It is the first  
> rule in alphabetical order, neither is the first rule in grammar file.
>
>
>
>
>
> From: antlr-interest-bounces at antlr.org [mailto:antlr-interest-bounces at antlr.org 
> ] On Behalf Of Jim Idle
> Sent: Wednesday, January 07, 2009 11:31 AM
> Cc: antlr-interest at antlr.org
> Subject: Re: [antlr-interest] expression parser example Expr.g dont  
> work
>
>
>
> Mats Ekberg wrote:
>
> I removed the NEWLINE requirement entierly and evaluates "expr" in  
> ANTLRWorks, same result. Sorry.
> The input "(1 + 2) * 3 - 4" (with a newline at the end) just  
> recognizes "( 1 + 2" and the nothing more.
>
>
> Place an EOF in the mix:
>
> stat : expr? EOF ;
>
> And fix your NEWLINE:
>
> NEWLINE: '\r'? '\n' { $channel = HIDDEN; } ;
>
>
> Then when you run ANTLR Works, make sure that you are choosing the  
> stat rule as the start rule (and use the debugger, not the  
> interpretter).
>
>
> Jim
>
>
>
> grammar Expr;
>
> expr
>     :   multExpr ( '+' multExpr | '-' multExpr )*
>     ;
>
> multExpr
>     :   atom ('*' atom )*
>     ;
>
> atom
>     :   INT
>     |   '(' expr ')'
>     ;
>
> INT :   '0'..'9'+ ;
> NEWLINE:'\r'? '\n' ;
> WS  :   (' '|'\t')+ {skip();} ;
>
> ons 2009-01-07 klockan 09:55 -0500 skrev Chris Snyder:
>
> stat:   expr NEWLINE
>
>
>
> looks like is should just be
>
>
>
> stat:   expr
>
>
>
> The current form hits the ‘(‘ and then looks for expr which  
> requires a NEWLINE after ‘2’ which you don’t have.
>
>
>
> I didn’t verify this though.
>
>
>
> C
>
>
>
> From:antlr-interest-bounces at antlr.org [mailto:antlr-interest-bounces at antlr.org 
> ] On Behalf Of Mats Ekberg
> Sent: Wednesday, January 07, 2009 1:22 AM
> To: antlr-interest at antlr.org
> Subject: [antlr-interest] expression parser example Expr.g dont work
>
>
>
>
> I have stripped the classical expr.g example and when I run it in  
> ANTLRWorks it dont work.
> The input "(1 + 2) * 3 - 4" (with a newline at the end) just  
> recognizes "( 1 + 2" and the nothing more.
> How come?
>
> grammar Expr;
>
> prog:   stat+ ;
>
> stat:   expr NEWLINE
>     |   NEWLINE
>     ;
>
> expr
>     :   multExpr ( '+' multExpr | '-' multExpr )*
>     ;
>
> multExpr
>     :   atom ('*' atom )*
>     ;
>
> atom
>     :   INT
>     |   '(' expr ')'
>     ;
>
> INT :   '0'..'9'+ ;
> NEWLINE:'\r'? '\n' ;
> WS  :   (' '|'\t')+ {skip();} ;
>
>
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