Re: missing 7th digit in float

Hi!

On Oct 20, [email protected] wrote:
> 
> Hi Sergei,
> 
> I won't say that the default of 6 is incorrect, but it's not what I
> expected because all I heard of the precision of floating point numbers
> till now is 7-8:
> from http://www.scri.fsu.edu/~jac/MAD3401/Backgrnd/ieee-sgl.html
> The 32-bit (single precision) IEEE floating-point representation ...This
> means we get a bit more than 7 decimal digit precision.
> C and Java use this standard definition.
> All other database systems I could check (M$ SQLserver and Borland
> Interbase) provide 7 significant digits for the float datatype as default
> (Interbase has no option for it's configuration).
> I don't know the reason for your decision, but I think a default of 7 would
> be better for interoperatibility or a change from another database to
> mysql.

MySQL uses architecture-dependent format for float/double.  Thus it also
uses architecture-dependent settings for float's precision.  In
particular, 6 comes from float.h (in /usr/include/, or
/lib/gcc-lib/i686-pc-linux-gnu/2.95.3/include/, or whatever), that
defines

#define FLT_DIG            6
 
Regards,
Sergei

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  /  |/  /_ __/ __/ __ \/ /   Sergei Golubchik <[email protected]>
 / /|_/ / // /\ \/ /_/ / /__  MySQL AB, Senior Software Developer
/_/  /_/\_, /___/\___\_\___/  Osnabrueck, Germany
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