RE: [HACKERS] floating point representation

[Hiroshi Inoue]

> -----Original Message----- > From: Tom Lane [mailto:[EMAIL PROTECTED]] > > Peter Eisentraut <[EMAIL PROTECTED]> writes: > > The GNU C library now offers a %a (and %A) format that prints floating > > point numbers in a semi-internal form that is meant to be portable. (I > > image this was done because of C99, but I'm speculating.) It might be > > useful to offer this to preserve accurate data across dumps. > [snip] > > So, it looks like C99-compliant libc implementations will have this, > but I'd hesitate to rely on it for pg_dump purposes; it would certainly > not be very portable for awhile yet. > Agreed. > Peter's idea of a SET variable to control float display format might > not be a bad idea, but what if anything should pg_dump do with it? > Maybe just crank the precision up a couple digits from the current > defaults? > Currently the precision of float display format is FLT_DIG(DBL_DIG). It's not sufficent to distinguish float values. As Peter already suggested, the quickest solution would be to change XXX_DIG constants to variables and provide a routine to SET the variables. Strictly speaking the precision needed to distigush float values seems OS-dependent. It seems preferable to have a symbol to specify the precision. Regards, Hiroshi Inoue