Has anyone bothered to actually look into the code?
regression=# select power(2::numeric,1000);
power
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
10715086071862673209484250490600018105614048117055336074437503883703510511249361224931983788156958581275946729175531468251871452856923140435984577574698574803934567774824230985421074605062371141877954182153046474983581941267398767559165543946077062914571196477686542167660429831652624386837205668069376.0000000000000000
(1 row)
AFAICT the only thing missing is a pg_operator entry linked to the
function.
regards, tom lane