$ Recursive
proc fact(n);
    if (n < 2) then
        return 1;
    else
        return n * fact(n - 1);
    end if;
end proc;

$ Iterative
proc factorial(n);
    v := 1;
    for i in {2..n} loop
        v *:= i;
    end loop;
    return v;
end proc;