Re: percentage discount not calculating properly

[Chris Travers <..hidden..>]

On Wed, Feb 24, 2010 at 1:13 AM, Luke <..hidden..> wrote:
> On Tue, 23 Feb 2010, Bob Miller wrote:
>
> See David's message for a supposed fix, but as for what's going on...:
>
>> One of my clients has recently noticed a slight peculiarity in the
>> percentage discount, and I have been able to verify it.
>> For example, sell 252 items at $1.05 with a 15% discount.  By my handy
>> dandy calculator application, 252*1.05*.85=224.91.  However, on the
>> invoice, the total calculated is $224.28.  It is a small difference,
>> however, it grows when more items are sold.  When we put on another
>
> Your math is not the math which the program does.  It does
> this:
> 1.05 * 0.85 * 252.  That would still be okay, until you show your work.
>
> 1.05 * 0.85 = 0.8925
> 0.8925 Internal round to 2 decimal places = 0.89
> 0.89 * 252 = 224.28
>

That's the way this is handled currently.

> This has bugged me to no end.  SL had a way to change the precision, but
> LSMB dropped it for reasons I knew not, and provided no workaround for
> this problem [until now].
>
The dropping was a side-effect of moving to BigFloats and managing
precision.  This was necessary to avoid some of the rounding bugs we
found in the code we inherited.  Unfortunately I am not sure there is
a straight-forward solution here due to the way precision is tracked.
 I am going to try to come up with a bug fix for it shortly, however.

Best Wishes,
Chris Travers