Re: CurrencyConverter not precise
Re: CurrencyConverter not precise
- Subject: Re: CurrencyConverter not precise
- From: Steffen Boerner <email@hidden>
- Date: Tue, 12 Dec 2006 14:49:10 +0000
Thanks, thats what I found as well. I mean if you need accuracy in a
financial application. There is no way around it unless you implement
it yourself.
Am 12.12.2006 um 14:47 schrieb Jim Thomason:
It might be worthwhile and a good exercise to try converting it to
something more precise, either an NSDecimal (C structure) or
NSDecimalNumber (objc wrapper). They're not as much fun to work with
(float a = b + c vs NSDecimalNumber* a = [b decimalNumberbyAdding:c]),
but they're more accurate and should get rid of the errors.
-Jim.....
On 12/12/06, Steffen Boerner <email@hidden> wrote:
Cool thanks, that should get me started.
Am 08.12.2006 um 22:27 schrieb Sherm Pendley:
> On Dec 8, 2006, at 4:42 PM, Steffen Börner wrote:
>
>> Hi List,
>>
>> This is my first post here.
>> I just followed Apples tutorial "Building Currency Converter"
>>
>> http://developer.apple.com/documentation/Cocoa/Conceptual/
>> ObjCTutorial/chapter05/chapter_5_section_1.html#//apple_ref/doc/
>> uid/20002053-TPXREF101
>>
>> But when entering values with digits after the decimal sign the
>> calculated amount is not precise.
>> For example:
>> Exchange Rate: 3.22
>> Dollars to Convert: 10
>> Amount in other Currency:32,20000076293945
>
> In a nutshell, what you've found is a limitation of storing
> floating-point numbers in a binary format. Just as 1/3 cannot be
> exactly represented as a decimal number, there are numbers that
> cannot be exactly represented in binary.
>
> "What Every Computer Scientist Should Know About Floating-point
> Arithmetic":
>
> <http://docs.sun.com/source/806-3568/ncg_goldberg.html>
>
> sherm--
>
> Web Hosting by West Virginians, for West Virginians: http://wv-
www.net
> Cocoa programming in Perl: http://camelbones.sourceforge.net
>
>
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