学步园

读loki有感，TYPEList原理
问题一，简化版的TYPEList，只支持int型
template<int n>
class TYPEList
{
public:
 int Head;
 TYPEList<n-1> Tail;

};

template<>
class TYPEList<0>
{
public:
 int Tail;
 int Head; 
};

测试代码
TYPEList<0> l0;
 l0.Head = 1;
 l0.Tail = 2;

TYPEList<2> l2;
l2.Head = 3;
l2.Tail.Head = 4;
l2.Tail.Tail.Head = 5;
l2.Tail.Tail.Tail = 6;

问题二：可以同过GetAt(int)获取值
template<int n>
class TYPEList
{
public:
 int Head;
 TYPEList<n-1> Tail;
 int GetAt(int index )
 {
  if( n+1 == index )
   return Head;
  return Tail.GetAt(index);
 }
};

template<>
class TYPEList<0>
{
public:
 int GetAt(int index)
 {
  if( 1 == index )
   return Tail;
  return Head;
 }
 int Tail;
 int Head; 
};
测试代码
TYPEList<0> l0;
 l0.Head = 1;
 l0.Tail = 2;

 TYPEList<2> l2;
 l2.Head = 3;
 l2.Tail.Head = 4;
 l2.Tail.Tail.Head = 5;
 l2.Tail.Tail.Tail = 6;

 int i1 = l2.GetAt(0);
 int i2 = l2.GetAt(1);
 int i3 = l2.GetAt(2);
 int i4 = l2.GetAt(3);

问题三，类型不再限于int,但最多集成3个变量。

class NullType
{
};

template <class T, class U>
struct Typelist
{
 T Head;
 U Tail;
};

template <typename T1  = NullType, typename T2  = NullType, typename T3  = NullType >

struct MakeTypelist
{ 
private:  
 typedef typename MakeTypelist< T2 ,T3>::Result TailResult; 
public:  
 typedef Typelist<T1, TailResult> Result; };

template<> 
struct MakeTypelist<> 
 {  
  typedef NullType Result;
 };

测试代码：
MakeTypelist<ULONG,CString,int>::Result User,User2;

 User.Head = 1;
 User.Tail.Head = "何志丹";
 User.Tail.Tail.Head = 35;

 User2 = User;

 template <class AtomicType, template <class> class GenFunc>
    struct IterateTypes
   {    template<class II>
    void operator()(II ii)
       {   
    GenFunc<AtomicType> genfunc;
        *ii = genfunc();
        ++ii; //Is this even needed?
        }
    };