This was the site that Reference corrections link moved me.
I think there is an error with abs(x):
Reference Language | Libraries | Comparison | Changes
Computes the absolute value of a number.
x: the number
x: if x is greater than or equal to 0.
-x: if x is less than 0. <-------------------Here
Compared to c++ reference: if x is less than 0, means negative number, returns x. (Not -x ! )