grammar Prefix;

@members {
    public static void main(String[] args) throws Exception {        
        PrefixLexer lex = new PrefixLexer(new ANTLRFileStream(args[0]));
       	CommonTokenStream tokens = new CommonTokenStream(lex);

        PrefixParser parser = new PrefixParser(tokens);
        try {
            parser.s();
        } catch (RecognitionException e)  {
            e.printStackTrace();
        }
    }
}

/*------------------------------------------------------------------
 * LEXER RULES
 *------------------------------------------------------------------*/

fragment DIGIT	:	'0'..'9' ;
NUM		:	(DIGIT)+;
PLUS		:	'+' ;
STAR		:	'*' ;
SPACE		:	' '        {skip();};
NL 		:	'\r'? '\n' {skip();};


/*------------------------------------------------------------------
 * PARSER RULES
 *------------------------------------------------------------------*/

s	:	expr {System.out.println($expr.v);}; 

expr	returns [int v]	:	PLUS t1=expr t2=expr {$v=$t1.v+$t2.v;}
			|	STAR t1=expr t2=expr {$v=$t1.v*$t2.v;}
			|	NUM {$v=Integer.parseInt($NUM.text);}
			;