Re: numeric precision when raising one numeric to

On Fri, 2005-05-20 at 12:03, Tom Lane wrote:
> "Jim C. Nasby" <decibel@decibel.org> writes:
> > Why are we allowing implicit casts from numeric to floating point?
>
> Because the SQL spec requires it.
>
>          2) If the data type of either operand of a dyadic arithmetic op-
>             erator is approximate numeric, then the data type of the re-
>             sult is approximate numeric.
>
> It doesn't say to throw an error for mixed-type arithmetic.
>
> Now it also says
>
>          1) If the data type of both operands of a dyadic arithmetic opera-
>             tor is exact numeric, then the data type of the result is exact
>             numeric, ...
>
> which you could take as requiring us to provide numeric equivalents of
> every floating-point operator, but I don't find that argument very
> convincing for operations that are inherently not going to give exact
> results.

Are you saying that the exponent operator will return inexact results?
OR talking about other operators

>  The spec demands exact results from addition, subtraction,
> and multiplication, but as soon as you get to division they punt; let
> alone transcendental functions.

If you're quoting the 92 spec, it seems to say that multiplication
precision is also implementation specific.

> But having said that, I don't have a problem with putting in a
> pg_operator entry for numeric_power.  And if someone wants to improve
> the scale factor calculations therein, go for it.

OK, I'm gonna look at it this weekend.  I might have some questions
before I really get anything working, this being my first real adventure
hacking pgsql.

> But so far there's
> been an extremely low signal-to-noise ratio in this thread ...

Really, I've found it quite informative.  I see no reason to insult the
people who've contributed to it.