Comparison of real numbers fails

I have two REAL fieldsdebit w/ value of G1436908.22 credits w/ value of G1436908.22The following code is entering IF block even though the values are same. Any thoughts //if(debits != totalcredit) OR if(debits NE totalcredit) echo('Debits and Credits are not equal. Please make corrections') return false end

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Sravan_Kudithipudi

Resubmitting ..I have two REAL fieldsdebit w/ value of G1436908.22credits w/ value of G1436908.22The following code is entering IF block even though the values are same. Any thoughts//if(debits != credits) ORif(debits NE credits) echo('Debits and Credits are not equal. Please make corrections') return falseend

Howard_Pell

Message from Howard Pell <hlpell@opentext.com> via eLink

eLink

Comparing floating-point numbers cannot bedone with an equality operator as the binary representation of floating-pointnumbers may not be exact. One would almost always subtract one number from theother and then test that the difference was within some specified range.

For example

If (abs(result – expectedResult)< 0.0001)

Do something

Else …

Hope this helps

Howard

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Howard Pell

Senior Technical Educator Liaison, SpecialProjects

Open Text Corporation

www.opentext.com

Office: (519) 888-7111 Ext. 2203

Mobile (519) 574-2248

From: eLinkDiscussion: LAPI Discussion [mailto:lapi@elinkkc.opentext.com]
Sent: 2009-May-29 1:27 PM
To: eLink Recipient
Subject: Comparison of realnumbers fails

Comparison of real numbers fails

Posted by welfar01user15 (Kudithipudi, Sravan) on 2009/05/29 13:26

I have two REAL fields

debit w/ value of G1436908.22
credits w/ value of G1436908.22

The following code is entering IF block even though the values are same. Any thoughts

//if(debits != totalcredit) OR
if(debits NE totalcredit)
@ @ echo('Debits and Credits are not equal. Please make corrections')
@ @ return false
end@ @ @ @
@ @ @ @

sıɹɥɔ

Message from Chris Webster <cwebster@opentext.com> via eLink

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">eLink

Hi Sravan,

(This is actually an OScript question, but I suspect many LAPI developers are also OScripters, so I'll address your question here.)

Values of type Real in OScript are double-precision floating point numbers. When working with floating point numbers, in any language on any computer, you need to be aware of the arithmetic involved in their operation. In particular you need to be aware that there is only a certain level of precision available. (OScript guarantees 15 digits worth.)

So, for your example, although it might appear that the two values are the same, they are probably not. Typically in scientific computing you don't compare real numbers with one another to determine equality. Instead you compare their difference to a small number, an epsilon. Given a small enough epsilon the numbers are considered equal. In financial computing you generally don't use floating point numbers; you either work in units that are appropriate (perhaps "milli-cents"), or you use types that have appropriate precision (e.g. BCD).

For the values you're working with it may be interesting to echo the value of "debits - totalcredit". For the program you're working on you may want to consider how these values are being generated and what the effects of floating point arithmetic might be having.

Hope this helps,

-chris

From: eLink Discussion: LAPI Discussion [mailto:lapi@elinkkc.opentext.com]
Sent: Friday, May 29, 2009 12:27 PM
To: eLink Recipient
Subject: Comparison of real numbers fails

Comparison of real numbers fails

Posted by welfar01user15 (Kudithipudi, Sravan) on 2009/05/29 13:26

I have two REAL fields

debit w/ value of G1436908.22
credits w/ value of G1436908.22

The following code is entering IF block even though the values are same. Any thoughts

//if(debits != totalcredit) OR
if(debits NE totalcredit)
@ @ echo('Debits and Credits are not equal. Please make corrections')
@ @ return false
end@ @ @ @
@ @ @ @