Just looking at the reference section for the abs() function and it tells me that abs() does the following;
Description Computes the absolute value of a number. Parameters x: the number Returns x: if x is greater than or equal to 0. -x: if x is less than 0.
Well, blow me down, I'm guessing the return value just returns the original value of x, regardless if it was less than zero. I do not recall abs() would ever return a negative value. Should this instead read something along the lines of;
Returns the absolute value of x |x| = abs(x)
example: abs(12) = 12 abs(-14) = 14
And while I'm at it, the link where it mentions the following;
Corrections, suggestions, and new documentation should be posted to the Forum.
The link on the word 'Forum' is to the 'Arduino Forum :: Development :: Other Software Development', why on Earth there I ask?