The “–” is a double unary operator. It’s used to change the sign of the value twice.
If you use them for numbers, it doesn’t make a lot of sense, because you will end with the same number that you had before the operation.
5 = -(-5)
This operator is a shorthand method to convert TRUE and FALSE to 1 and 0.
-TRUE = -1 --TRUE = --1 = 1 -FALSE = 0 --FALSE = 0
You can use only one minus for FALSE because zero is neither a positive or a negative number.