Re: float output precision questions

Added to TODO:
* Add GUC variables extra_float_digits and extra_double_digitsto control output digits

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Tom Lane wrote:
> "Pedro M. Ferreira" <pfrazao@ualg.pt> writes:
> > Have two parameters, say DOUBLE_OUTPUT and EXTRA_DIGITS. DOUBLE_OUTPUT 
> > would select from decimal output or normalized output. EXTRA_DIGITS 
> > would add the required extra digits, from 0 (default) to 3,  when output 
> > is decimal.
> 
> I'm not happy with adding the hex-output option, since it's not
> very portable and doesn't seem necessary to solve the problem anyway.
> 
> But I think an EXTRA_DIGITS setting might be interesting.  In
> particular, suppose we allowed EXTRA_DIGITS to be negative?  Setting
> it to -1 or -2 would go a long way towards eliminating our problems
> with platform variations in the geometry regression test.
> 
> Perhaps something like
> 
> extra_float_digits    int    range -2 to 2, default 0
> 
> extra_float_digits adjusts the number of digits displayed for float4 and
> float8 output; the base value of 0 means we output FLT_DIG or DBL_DIG
> digits respectively.
> 
> Per discussion, there's no reason to allow a value greater than 2, but
> I'm not as sure what the lower limit should be --- maybe there's some
> use in setting it less than -2?
> 
>             regards, tom lane
> 
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