OpenEuphoria

Re: rounding problem

• Posted by Ricardo M. Forno <rmforno at tutopia.com> Oct 23, 2006
• 499 views

George Walters wrote:
> 
> 
> Using EU 2.4 and Win32
> 
> IF I trace and display the value of temp (a variable) the display shows
> temp = .7149999738
> 
> sprintf("%10.4f, temp)  displays .7150 which is not correct if its value is
> .7149999738
> 
> On the data base (mysql) the value displayed is .7150.
> 
> I need to solve this riddle since I'm having invoice totals incorrect. So
> how does sprintf know that .7150 is the value but yet .7149999738 is 
> displayed on the trace?? I"m confused.

Actually, 0.7150 is correct for 0.7149999738 since you specified it to be
4 digits (i.e., rounded to 4 digits).
If you are using floating numbers for invoicing, you'll found nearly
impossible to get exact results.
This is a property of floating numbers, the hardware, and the binary
and decimal arithmetics; Euphoria isn't guilty.
Solution: if you want results with 4 decimals, for example, use integers
that are 10,000 times greater than the original numbers. Round or truncate
them by means of the float() function [truncate: z = floor(x * 10000); round:
floor(x * 10000 + 0.5)]. When printing them, divide them into 10,000,
only for the task of showing them, not to further compute results.
In other words: if you want exact results using cents, then operate
with cents.
Regards.