ArcTan(x,y)?

[StephenG1CMZ]

(04-05-2017 08:10 PM)KeithB Wrote:  Harbison and Steele.

Except if x and y are 0, what angle should you return?

Judging by the reviews, H&S looks like a useful update of K&R.

Most of my programming has been functional, with the emphasis on returning real-world values.
I'd be looking for:
(A) Values not significantly different from atan2(0 .000001,0.00001) etc., assuming the 0 is a rounding error - no discontinuous jumps.
(B) Values that are portable and compatible. Every atan2 that I have seen since the 1980's has used 0, so I would need some convincing that a different incompatible value were useful.
(C) For real-world use: In the case of Atan2, I don't see 0,0 as being a real domain error, assuming the 0,0 was a rounding error from valid inputs like 0.001,0.001...what the pilot wants to see is an angle... I'd keep domain error for truly exceptional error conditions, like if the input (0,0) were instead (NaN,NaN) because the compass had dropped off, and you really cannot return an angle.
(D) But in maths class, I would like to see it highlighted as indeterminate.