part (-expression, 0) => "neg"

[compsystems]

HELLO BP, there is a problem extracting the operator from the following expression
the part (-3 * x, 0) extracts the minus sign "-", must extract the change of sign "neg" of the operator, so that the reverse process can be carried out, or make a difference between the symbols − (minus), - (neg)

[parisse]

- is neg, you won't see binary minus because a-b is internally a+(-b).