(-) precedence

[Thomas Okken]

(12-23-2022 12:02 AM)Albert Chan Wrote:  Hi, ijabbott

If we pickup tokens in reversed order, "precedence inversion" / "not making sense" does not happen.

How to distinguish subtraction from negation

Quote:If you can subtract, do it; if you can’t, then take it as a negation. Subtraction has priority.

Scanning backward, it will handle (op +/-) without issue.

2^-3^4
2^-(3^4)
2^(-(3^4))

2*-3/4
(2*-3)/4
(2*(-3))/4

Scanning backward is not necessary for this. Whether a + or - is unary or binary is unambiguously clear from when it is found during parsing: if it is found while looking for a subexpression, then it is unary, else it is binary. And what follows is parsed as an additive term in both cases.