Rounding error

[D-Man]

On Thu, Apr 05, 2001 at 09:58:05AM +1200, Matthew wrote:
| Hi,
| 
| I'm calculating a bunch of co-ordinates as below. I'm using
| Round(<coord>,2) but as you can see rounding errors are happening...

| How do I overcome this? I'm using ActivePython Build203.

Don't use FP.  Floating point is inherently inaccurate.  You said they
are co-ordinates,  2-d or 3-d?  I would recommend creating a Point
class, something along the lines of:

class Point :
    def __init__( xn , xd , yn , yd ) :
       self.xn = xn
       self.xd = xd
       self.yn = yn
       self.yd = yd

    ...


where xn is the integer part and xd is the decimal part.  Both should
be integers.  Do the rounding yourself on the [xy]d parts if you
really want it rounded (mod 100 should work for that, but check for
overflow and handle it properly).

HTH,
-D