Re: Bug #534: factorial function

pgsql-bugs@postgresql.org wrote:
> Janko Richter (j.richter@wallstreet-develop.de) reports a bug
> with a severity of 3 The lower the number the more severe it
> is.
>
> Short Description factorial function
>
> Long Description 1. The factorial function returns 0 when the
> argument is 0. The factorial Funtion is defined as:  factorial(0)=1

I have fixed factorial(0)=1 in 7.3.

> 2. It would be better to define a factorial function returning
> double precision. The factorial function returning bigint produces
> false values  with arguments larger then 20.
>
> Notice: I'm using the factorial function for statistical functions
> (for example poisson distribution)
>
> Thank you.
>
>
> Sample Code test=# select factorial(0);
>  factorial -----------
>     0
> (1 row)
>
> janko=# select factorial(21::bigint);
>  factorial ----------------------
>  -4249290049419214848 (1 row)

The problem here is that we don't have a bigint version of factorial,
just an int8 version.  This is now on the TODO list:

    * Change factorial to return a numeric

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