Re: A Newbie Float Problem
Re: A Newbie Float Problem
- Subject: Re: A Newbie Float Problem
- From: Shawn Erickson <email@hidden>
- Date: Fri, 16 Dec 2005 09:38:54 -0800
On 12/15/05, Jonathan Faulkenberry <email@hidden> wrote:
>
Hi all,
>
I am relatively new to Cocoa, although I have some experience with
>
some basic C. For some reason though, I am having trouble creating a
>
small app I am using to help me learn Cocoa. This app is supposed to
>
hold a float value named "money" an have two buttons, one which will
>
call addMoney: (which will add 5 to the float value) and one called
>
drink: (which will decrease the float value by 5). For some reason,
>
when I click on the button that calls addMoney:, the value of the
>
float goes to like a 10 digit number.
Others pointed out the incorrect format statement you are using.
To get a better understand of printf style formats review man 3 printf
or visit the following...
<
http://developer.apple.com/documentation/Darwin/Reference/ManPages/man3/printf.3.html>
<
http://developer.apple.com/documentation/Cocoa/Conceptual/DataFormatting/Articles/FormatStrings.html>
...with that said using floats for money calculations (etc.) can
result in unexpected precision errors that could confuse you and/or
customers. The following is from a Java perspective but I found it to
be the easiest document that covers the issue I am attempting to point
out to you...
<
http://java.sun.com/developer/JDCTechTips/2001/tt0807.html#tip1>
After reading the above consider NSDecimal (akin to BigDecimal in Java)...
<
http://developer.apple.com/documentation/Cocoa/Conceptual/NumbersandValues/index.html#//apple_ref/doc/uid/10000038i>
<
http://developer.apple.com/documentation/Cocoa/Reference/Foundation/ObjC_classic/Classes/NSDecimalNumber_index.html>
-Shawn
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