ArcTan(x,y)?

[StephenG1CMZ]

(04-09-2017 09:50 AM)JMB Wrote:  

(04-06-2017 03:30 PM)StephenG1CMZ Wrote:  Clearly, discontinuities near 0 cannot be avoided - I have even seen it suggested online that one could scale values and use integer arithmetic to work around. I am beginning to wonder whether returning an error might be useful. But many Atan2 implementations do return 0, so changing to return 45 instead would introduce compatibility issues.

The PRIME function polar_coordinates, also works in a similar way:

polar_coordinates(1,1) returns: [1.41421356237 45]

polar_coordinates(0.001,0.001) returns: [1.41421356237ᴇ−3 45]

polar_coordinates(0,0) returns: [0 0]

Interesting.

Arctan returns an angle.

It was only after Debugging why polar_coordinates sometimes doesnt return at all that I realised polar_coordinates returns a pair of values instead (I know, the plural "coordinates" should have been a clue) - which explains why something goes wrong if you assign it to a global rather than local variable...

Code:



 LOCAL XY:=0.0001;
 LOCAL II;
 LOCAL KK:=3;

 PC(XX,YY)
 BEGIN
  PRINT("PC");
  FOR II FROM 1 TO KK DO
   PRINT(II);
   XY:=polar_coordinates(1+2*);
   A:=polar_coordinates(1+2*);//STALLS
   PRINT(II);

  END;
  RETURN 1;
 END;

 EXPORT TNBUG() 
 BEGIN
  PRINT();
  PRINT(TEVAL(N:=PC(XY,XY)));
  PRINT("STALLS"); 
 END;

I was trying to time which of the three alternatives was slower, and I'm still waiting for polar_coordinates to finish the race [Android version]