4+5 |
plus(4,5) |
expr = left, op, right . @left = number . @right = number . -number = ["0"-"9"]+ . @op = plus | minus . -plus = "+" . -minus = "-" . |
expr = op,-"(",left,-",",right,-")" . @left = number . @right = number . -number = ["0"-"9"]+ . @op = plus | minus . -plus = -"plus", +"+" . -minus = -"minus", +"-" . |
<expr left="4" op="+" right="5"/>