factorial function/phase out postfix operators?

There have been occasional discussions about deprecating or phasing out 
postfix operators, to make various things easier in the parser.

The first step would in any case be to provide alternatives for the 
existing postfix operators.  There is currently one, namely the numeric 
factorial operator "!".  A sensible alternative for that would be 
providing a function factorial(numeric) -- and that already exists but 
is not documented.  (Note that the operator is mapped to proname 
"numeric_fac".  The function "factorial" maps to the same prosrc but is 
otherwise independent of the operator.)

So I suggest that we add that function to the documentation.

(Some adjacent cleanup work might also be in order.  The test cases for 
factorial are currently in int4.sql, but all the factorial functionality 
was moved to numeric a long time ago.)

What are the thoughts about then marking the postfix operator deprecated 
and eventually removing it?

-- 
Peter Eisentraut              http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services