How would you write a non-recursive algorithm to calculate factorials?

Question

How would you write a non-recursive algorithm to compute n!?

Answer 1

At run time this is non-recursive. At compile time it is recursive. Run-time performance should be O(1).

//Note: many compilers have an upper limit on the number of recursive templates allowed.

template 
struct Factorial 
{
    enum { value = N * Factorial::value };
};

template <>
struct Factorial<0> 
{
    enum { value = 1 };
};

// Factorial<4>::value == 24
// Factorial<0>::value == 1
void foo()
{
    int x = Factorial<4>::value; // == 24
    int y = Factorial<0>::value; // == 1
}