>
>Of course... that formula you gave has a risk of numeric overflow...

The formula I gave was

N = -N

I find one exception where the negative value results in the same value.

I'm not convinced overflow comes in

(1) the value is -2^31 and (2) you force the value to be contained in a 4 byte signed integer

n = 0x80000000
?'n = ', n	&& 2147483648
?'-n = ', -n	&& -2147483648
n = bitor(n, 0) && force a 4 byte signed integer
?'bitor = ', n	&& -2147483648
x = -n
?'-n = ', x	&& -2147483648
?'abs', abs(n)	&& -2.1474E+9

? ' x == -x ', x == -x  && TRUE

Update - and yes - I know why