Calculating and printing factorial at compile time in C++

Question

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

template<>
struct Factorial<0> {
    enum {val         


        

Answer 1

i am learning basics of TMP, and want to know the result at compile to make sure logic is correct.

In that case, what you really want is a static assertion:

static_assert(Factorial<5> ::value ==     120,  "5! should be 120");
static_assert(Factorial<10>::value == 3628800, "10! should be 3628800");

If your compiler does not support static_assert yet, you can use BOOST_STATIC_ASSERT.