Re: Arbitrary precision arithmatic with pgsql

On 8/31/2004 11:04 AM, Tom Lane wrote:

> Jan Wieck <JanWieck(at)Yahoo(dot)com> writes:
>> I agree that doing
>> select 2::numeric ^ 100;
>> should emit some sort of a warning.
>
> I do not. The conversion of 2::numeric to float is exact, so AFAICS
> the only way to do that would be to make *every* coercion of numeric to
> float emit a warning. This is not a reasonable response to the fact
> that Rajesh is unaware of the set of available operators. Moreover
> it would essentially break float constants (since "2.0" starts life
> as numeric and is only cast to float when the context demands).

I thought they start life as an unknown literal ... that of course
changes things.

Jan

>
> I'd be in favor of adding a numeric^numeric operator to ease access to
> the existing pow() code, but I'm not sure this makes the issue go away
> entirely. It looks like "select 2 ^ 100" would still default to being
> a float operation.
>
> regression=# create operator ^ (procedure=pow, leftarg=numeric, rightarg=numeric);
> CREATE OPERATOR
> regression=# select 2::numeric ^ 100;
> ?column?
> --------------------------------------------------
> 1267650600228229401496703205376.0000000000000000
> (1 row)
>
> regression=# select 2 ^ 100;
> ?column?
> ----------------------
> 1.26765060022823e+30
> (1 row)
>
> regression=# select 2.0 ^ 100;
> ?column?
> --------------------------------------------------
> 1267650600228229401496703205376.0000000000000000
> (1 row)
>
>
> regards, tom lane

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