Bug #534: factorial function

Janko Richter (j(dot)richter(at)wallstreet-develop(dot)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

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)

No file was uploaded with this report