
fact - factorial function

Calling sequence:
fact(integer)

Parameter:

integer   --  non-negative integer

Overloading:

all

Summary:

fact is the usual factorial function that, when fact(n) is called, returns the
product of the integers from 1 to n. fact returns an error when the argument
integer is an number but not a non-negative integer.  fact returns the
function call with evaluated arguments, if the argument cannot be evaluated
to a number. fact is a kernel function.

>>  fact(20);

     2432902008176640000

