[antlr-interest] Interesting problem with labels in V4b1
Eric
researcher0x00 at gmail.com
Sat Sep 22 15:03:12 PDT 2012
Hi Mike,
Just giving it a quick syntactic look it looks like the vertical bar before
'^' is an exclamation point.
Eric
On Sat, Sep 22, 2012 at 5:56 PM, Mike Cargal <mike at cargal.net> wrote:
> This:
>
> grammar Foo;
> expr : '(' expr ')' # parenExpr
> | '%' expr # pctExpr
> ! '^' expr # expnExpr
> | expr ('*'|'/') expr # multExpr
> | expr ('+'|'-') expr # addExpr
> ;
> gives me the following errors…
> error(50): Foo.g4:4:16: mismatched input ''^'' expecting SEMI while
> matching a rule
> error(50): Foo.g4:4:37: '#' came as a complete surprise to me while
> matching rule preamble
>
>
> This:
>
> grammar Foo;
> expr : '(' expr ')' # parenExpr
> | '%' expr # pctExpr
> // ! '^' expr # expnExpr
> | expr ('*'|'/') expr # multExpr
> | expr ('+'|'-') expr # addExpr
> ;
>
> generates without error
>
> and this:
>
> grammar Foo;
> expr : '(' expr ')'
> | '%' expr
> ! '^' expr
> | expr ('*'|'/') expr
> | expr ('+'|'-') expr
> ;
>
> generates without error
>
> all compiled using:
> java -jar /usr/local/lib/antlr-4.0b1-complete.jar -visitor Foo.g4
>
> Somehow the exponentiation expression is a problem if and only if I'm
> using labels.
>
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