I want to be able to parse expressions like -5 and -(2 + 3 * 4). At the moment, I'm doing this with two separate rules, but since -5 is the same as -(5) I want to be able to use the same rule for both situations as the parentheses in -5 are implicit. In PLY, there is the nonassoc precedence, so I was wondering if such a thing also existed in RPLY?