Definitions

   The factorial of   0   (zero)   is defined as being   1   (unity).
   The   Factorial Function   of a positive integer,    n,    is defined as the product of the sequence:
                 n,   n-1,   n-2,   ...   1 



Task

Write a function to return the factorial of a number.

Solutions can be iterative or recursive.

Support for trapping negative    n    errors is optional.



Related task

   Primorial numbers


// recursive
sub factorial(n)
    if n > 1 then return n * factorial(n - 1) else return 1 end if
end sub
 
//iterative
sub factorial2(n)
    local i, t
 
    t = 1
    for i = 1 to n
        t = t * i
    next
    return t
end sub
 
for n = 0 to 9
    print "Factorial(", n, ") = ", factorial(n)
next