Re: float & double scanner question
Re: float & double scanner question
- Subject: Re: float & double scanner question
- From: Clark Cox <email@hidden>
- Date: Fri, 31 Dec 2004 16:43:01 -0500
Try to write 1.555 using the sum of only powers of two, and you'll see
the issue (it cannot be done in a finite number of digits). In binary,
1.555 would be approx: 1.1000111000010100011...(continues on for
infinity)
This is the same reason that one cannot write the value of 1/3 in a
finite number of decimal digits.
On Fri, 31 Dec 2004 13:18:23 -0800, Mark Dawson <email@hidden> wrote:
> doing a "[scanner scanDouble:&val] on the string "1.555" sets the "val"
> to 1.554999999…, "1.55" to 1.55.
>
> scanFloat on "1.55" set its to 1.54999995, "1.555" to 1.5549999995
>
> While I know there are precision issues with floats and doubles, I
> can't understand why a "1.55" number can't be converted "cleanly". It
> seems like these numbers should be way within the precision boundaries
> of a float precision. Am I missing something?
>
> Thanks,
>
> Mark
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--
Clark S. Cox III
email@hidden
http://www.livejournal.com/users/clarkcox3/
http://homepage.mac.com/clarkcox3/
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