Compile-time constant id

Question

Given the following:

template
class A
{
public:
    static const unsigned int ID = ?;
};

I want ID to generate a unique c

Answer 1

Here is a C++ code that uses __DATE__ and __TIME__ macro to get unique identifiers for types

Format:

// __DATE__ "??? ?? ????"
// __TIME__ "??:??:??"

This is a poor quality hash function:

#define HASH_A 8416451
#define HASH_B 11368711
#define HASH_SEED 9796691    \
+ __DATE__[0x0] * 389        \
+ __DATE__[0x1] * 82421      \
+ __DATE__[0x2] * 1003141    \
+ __DATE__[0x4] * 1463339    \
+ __DATE__[0x5] * 2883371    \
+ __DATE__[0x7] * 4708387    \
+ __DATE__[0x8] * 4709213    \
+ __DATE__[0x9] * 6500209    \
+ __DATE__[0xA] * 6500231    \
+ __TIME__[0x0] * 7071997    \
+ __TIME__[0x1] * 10221293   \
+ __TIME__[0x3] * 10716197   \
+ __TIME__[0x4] * 10913537   \
+ __TIME__[0x6] * 14346811   \
+ __TIME__[0x7] * 15485863

unsigned HASH_STATE = HASH_SEED;
unsigned HASH() {
    return HASH_STATE = HASH_STATE * HASH_A % HASH_B;
}

Using the hash function:

template 
class A
{
public:
    static const unsigned int ID;
};

template <>
const unsigned int A::ID = HASH();

template <>
const unsigned int A::ID = HASH();

template <>
const unsigned int A::ID = HASH();

template <>
const unsigned int A::ID = HASH();

#include 

int main() {
    std::cout << A::ID << std::endl;
    std::cout << A::ID << std::endl;
    std::cout << A::ID << std::endl;
    std::cout << A::ID << std::endl;
}