Re: [HACKERS] 123.45 - 123 = 0.45

Bruce Momjian <maillist@candle.pha.pa.us>

From: Bruce Momjian <maillist@candle.pha.pa.us>
To: daveh@insightdist.com (David Hartwig)
Cc: sferac@bo.nettuno.it, pgsql-hackers@postgreSQL.org
Date: 1998-12-15T16:20:15Z
Lists: pgsql-hackers
> Try this:
> 
> #include <stdio.h>
> 
> main()
> {
> double f1 = 123.45;
> double f2 = 123.00;
> double r;
> 
>     r = f1 - f2;
>     printf("%0.15f  %0.15f  %0.15f\n", f1, f2, r);
> }
> 
> Internal representation of 123.45 is not exact.   In the conversion to
> binary, an irrational number is created which is truncated to 64 bits.

Yes, someone pointed this out to me in private e-mail, and I wrote a C
program to confirm it.  I just had never seen such rounding on such
small non-irrational numbers.

-- 
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