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Floating point arithm. inaccuracy is handled inconsistently

Description

Hi,

There seems to be an inconsistency between output and internal handling of floating point arithmetic results.
Example:

<cfset MyVar = 2807.75 - 2801.1 - 6.65 /> <cfoutput> Value of MyVar: #MyVar# <br /> <cfif MyVar eq 0> It's zero <cfelse> It's NOT zero </cfif> </cfoutput>

Output in Lucee:

Value of MyVar: 0 It's NOT zero

Output in AdobeCF:

Value of MyVar: 9.05941988094E-014 It's NOT zero

Lucee's behavior of outputting a rounded value but not using it during comparisons is rather frustrating during debugging.
BTW putting a Val() around MyVar does make it equal to 0 in Lucee (but not in AdobeCF).

Regards,
Florian

Environment

Windows 2008R2, Java 1.7.0_75, Tomcat7

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Pothys - MitrahSoft 20 April 2022 at 15:02
Edited

Due to this issue in arithmetic operation with float numbers affects the isvalid(integer) behaviour and makes confusion in result https://luceeserver.atlassian.net/browse/LDEV-3926

Gunnar Lieb 8 October 2021 at 09:56

This is the most current discussion on the mailing list https://dev.lucee.org/t/bug-number-multiplication-and-99999999999/9010/13

Gunnar Lieb 8 October 2021 at 09:52

Wow, I’m surprised that this hasn’t been addressed for such a long time. For me it’s a major issue, at least if you deal with financial calculations!

Michael Offner 25 January 2016 at 16:42

when we cast numbers to a string, what happens when you output a number we avoid to use scientific format, because we learned that this bring more harm than good in most cases.
So it is only about converting the number to a string, nothing else.
Workaround:

#MyVar.toString()# // you can avoid it by calling to String

you should also consider to use the function "PrecisionEvaluate" (in Lucee and ACF) when you need precise results of math operations.

<cfset MyVar = PrecisionEvaluate("2807.75 - 2801.1 - 6.65") />

This will give you the right result in this case with Lucee and ACF.

We plan for some time to make it possible that Lucee is using a more percise math outside the function "PrecisionEvaluate", sadly this needs a lot of changes in Lucee and needs a lot of time to do.

Coming back to this ticket it would make sense to have an admin/application.cfc setting for this.

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Affects versions

Created 23 November 2015 at 16:51
Updated 8 June 2022 at 14:09