尼采的神奇 Functor

尼采給我的題目...不如在此發表答案.

#include <iostream>

typedef int (*Functor)();

// Recursive type template that generate a
// compile-time list of Functor using inheritance
template<size_t N> struct Unit : public Unit<N-1> {
  Unit() : mFunctor(&Unit<N>::fun) {}
  static int fun() { return N; }
  Functor mFunctor;
};

// Partial specialization to end the recursion
template<> struct Unit<0> {
  Unit() : mFunctor(&Unit<0>::fun) {}
  static int fun() { return 0; }
  Functor mFunctor;
};

// Partial specialization to reduce recursive template complexity
template<> struct Unit<256> : public Unit<255> {
  Unit() : mFunctor(&Unit::fun) {}
  static int fun() { return 256; }
  Functor mFunctor;
};

// Partial specialization to reduce recursive template complexity
template<> struct Unit<512> : public Unit<511> {
  Unit() : mFunctor(&Unit::fun) {}
  static int fun() { return 512; }
  Functor mFunctor;
};

// A compile-time maximum count of Functor
static const size_t cMaxN = 768;

typedef Unit<cMaxN> List;
static const List cList;

// A function that return a Functor that return i.
// In other words, it selects from a list of compile-time functors
// base on the run-time parameter i.
Functor getFunctor(int i) {
  {  // We have the assumption that Unit<> struct are packed tightly together in cList
    typedef const char* byte_ptr;
    byte_ptr functorAddres1 = byte_ptr(&(static_cast<const Unit<1>*>(&cList)->mFunctor));
    byte_ptr functorAddres2 = byte_ptr(&(static_cast<const Unit<2>*>(&cList)->mFunctor));
    (void)functorAddres1;  (void)functorAddres2;
    assert(functorAddres2 - functorAddres1 == sizeof(Functor));
  }
  assert(i <= cMaxN);
  return *((Functor*)(&cList) + i);
}

int main() {
  for(size_t i=0; i<=cMaxN; ++i) {
    Functor f = getFunctor(i);
    std::cout << f() << std::endl;
    assert(f() == int(i));
  }

  return 0;
}

Win少, 我的答案正確嗎?