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Re: Precision of doubles and stdio
- From: Jim Easton <jim at cs dot ualberta dot ca>
- To: Roberto Bagnara <bagnara at cs dot unipr dot it>
- Cc: cygwin at cygwin dot com, Jim Easton <jim at cs dot ualberta dot ca>
- Date: Mon, 6 Mar 2006 01:27:51 -0700 (MST)
- Subject: Re: Precision of doubles and stdio
Dear Mr. Bagnara,
Roberto Bagnara wrote:
...
> does this on Linux/i686
>
> $ a.out
> 70.9
> 70.900000000000005684341886080801486968994140625
>
> and does the following under Cygwin on the same machine:
...
> $ ./a.exe
> 70.9
> 70.90000000000000568434188608080148696899414
>
> Why? Is there a way to reconcile the two behaviors?
> Notice that I know about the x87 and its vaguaries:
> nonetheless I wonder why such a scanf immediately
> followed by a printf shows a difference between
> Cygwin and Linux.
With all due respect, why would you want to? With double you are
guaranteed only 16 or so digits - the rest is noise. Frankly I am
amazed that it agrees as far as it does.
Jim
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