[antlr-interest] trouble running Antlr on grammar file

[Kumar, Rajesh (Systems) UTRC]

Hi everyone,

I created a simple expression grammar in a .g file. I checked it with Antlrworks to see that there were no errors in the grammar.  The grammar is the following:

****************
grammar		 Expression; 

prog	:	 exp
	;
	
exp	: '(' exp ')' exp_t
	| atomic_expr exp_t
	| '!' atomic_expr exp_t
	;
	
exp_t	: '->' exp exp_t 
	| '&&' exp exp_t 
	| '||' exp exp_t
	|
	;

atomic_expr
	:	 ID
	|	'Unavailable' '(' GEN ')'
	|	'Powers' '(' GEN ',' ID ')'
	|       'OnlyAvailable' '(' GEN ')'
	;

ID	:	 ('a'..'z'|'A'..'Z')('a'..'z'|'A'..'Z'|'0'..'9')*
	;

NUM	:	('0'..'9')+
	;
	
GEN	:     'X_L1'
	|	'X_L2'
	|	'X_R1' 
	;
	
WS	:	(' '|'\t')+ {skip();};
********************

When I run "java antlr.Tool Expression.g" I get the following 

ANTLR Parser Generator   Version 2.7.7 (20060906)   1989-2005
Expression.g:1:1: unexpected token: grammar
error: Token stream error reading grammar(s):
Expression.g:11:13: expecting ''', found '>'
Expression.g:1:1: rule grammar trapped:
Expression.g:1:1: unexpected token: grammar
TokenStreamException: expecting ''', found '>'

Can anyone help me out?
Thanks.
Rajesh