PARSER_BEGIN(prefix) public class prefix { } PARSER_END(prefix) SKIP : { " " | "\n" } TOKEN : { < PLUS: "+"> | < MINUS: "-"> | < TIMES: "*"> | < DIVIDE: "/"> | < INTEGER_LITERAL: (["0"-"9"])+ > } void expression(): {} { (<PLUS> | <MINUS> | <TIMES> | <DIVIDE>) expression() expression() | <INTEGER_LITERAL> }