Package SimpleMath; Tokens l_paren = '('; r_paren = ')'; plus = '+'; minus = '-'; mult = '*'; div = '/'; number = ['0'..'9']+; blank = [' ' 9 12 8 11 13 10]; Ignored Tokens blank; Productions expr = {term} term | {plus} expr plus term | {minus} expr minus term ; term = {factor} factor | {mult} term mult factor | {div} term div factor ; factor = {number} number | {expr} l_paren expr r_paren ;