用模板的偏特化和成員模板，重載函數(shù)調(diào)用運(yùn)算符成功的實(shí)現(xiàn)了delegate,既可以綁定普通函數(shù)，也可以綁定對(duì)象及其成員函數(shù)
在cygnuwin下編譯通過, 
還不支持一個(gè)delegate包含多個(gè)函數(shù)的用法,不過相信很簡單，從std::list派生一個(gè)類 
就可以了 
我用的cygun有些毛病， 
my_delegate d2=my_delegate(t,&Test::f); 
                           ^如果寫成&t，就會(huì)導(dǎo)致編譯器內(nèi)部錯(cuò)誤，沒辦法了 
  
我本來寫程序是加空行的，貼到BBS上就沒了，忍受一下吧 
Win32下的各種調(diào)用約定很討厭，沒有考慮，不過實(shí)現(xiàn)起來不費(fèi)什么腦筋，就是麻煩， 
不管了 
  
// Test.cpp : Defines the entry point for the console application. 
// 
#include <stddef.h> 
template<class T> 

//函數(shù)traits,用來提取函數(shù)的返回類型

struct function_traits 
{ 
}; 
template<class RT> 
struct function_traits< RT(*)() > 
{ 
 typedef RT result_type; 
}; 
template<class RT,class AT> 
struct function_traits< RT(*)(AT) > 
{ 
 typedef RT result_type; 
 typedef AT argument_type; 
}; 
template<class RT,class AT1,class AT2> 
struct function_traits< RT(*)(AT1,AT2) > 
{ 
 typedef RT result_type; 
 typedef AT1 first_argument_type; 
 typedef AT2 second_argument_type; 
};

// 函數(shù)traits,用來提取類成員函數(shù)的返回類型

template<class RT, class OT> 
struct function_traits< RT (OT::*)() > 
{ 
 typedef OT object_type; 
 typedef RT result_type; 
}; 
template<class RT, class OT, class AT> 
struct function_traits< RT (OT::*)(AT) > 
{ 
 typedef OT object_type; 
 typedef RT result_type; 
 typedef AT argument_type; 
  
 typedef AT first_argument_type; 
}; 
template<class RT,class OT,class AT1,class AT2> 
struct function_traits< RT (OT::*)(AT1,AT2) > 
{ 
 typedef OT object_type; 
 typedef RT result_type; 
 typedef AT1 first_argument_type; 
 typedef AT2 second_argument_type; 
};

// 把一個(gè)普通函數(shù)類向轉(zhuǎn)化為類型兼容的指定類的成員函數(shù)類型 
template <typename OT, typename PFT> 
struct to_member_function_pointer 
{ 
}; 
template <typename OT,typename RT> 
struct to_member_function_pointer< OT, RT(*)() > 
{ 
 typedef RT (OT::*type)(); 
}; 
template <typename OT, typename RT, typename AT> 
struct to_member_function_pointer< OT, RT(*)(AT) > 
{ 
 typedef RT (OT::*type)(AT); 
}; 
template <typename OT, typename RT, typename AT1, typename AT2> 
struct to_member_function_pointer< OT, RT(*)(AT1,AT2) > 
{ 
 typedef RT (OT::*type)(AT1,AT2); 
}; 
template <typename OT, typename RT, typename AT1, typename AT2, typename AT3> 
struct to_member_function_pointer< OT, RT(*)(AT1,AT2,AT3) > 
{ 
 typedef RT (OT::*type)(AT1,AT2,AT3); 
}; 

// 轉(zhuǎn)化為const 成員函數(shù)

template <typename OT, typename PFT> 
struct to_const_member_function_pointer 
{ 
}; 
template <typename OT, typename RT> 
struct to_const_member_function_pointer< OT, RT(*)() > 
{ 
 typedef RT (OT::*type)() const; 
}; 
template <typename OT, typename RT, typename AT> 
struct to_const_member_function_pointer< OT, RT(*)(AT) > 
{ 
 typedef RT (OT::*type)(AT) const; 
}; 
template <typename OT, typename RT, typename AT1, typename AT2> 
struct to_const_member_function_pointer< OT, RT(*)(AT1,AT2) > 
{ 
 typedef RT (OT::*type)(AT1,AT2) const; 
}; 
template <typename OT, typename RT, typename AT1, typename AT2, typename AT3> 
struct to_const_member_function_pointer< OT, RT(*)(AT1,AT2,AT3) > 
{ 
 typedef RT (OT::*type)(AT1,AT2,AT3) const; 
}; 

// delegate的實(shí)現(xiàn)

template <typename PFT> 
class delegate 
{ 
 class object 
 { 
 }*m_pObject; // 對(duì)象指針，是一個(gè)代理對(duì)象
 typedef typename to_member_function_pointer<object, PFT>::type object_member_fuunction_pointer; 
 union 
 { 
  PFT m_pf; 
  object_member_function_pointer m_pmf; 
 }; // 函數(shù)指針和成員函數(shù)指針的聯(lián)合體
 public: 
  typedef typename function_traits<PFT>::result_type result_type; 
  
  delegate() 
  { 
   m_pObject=NULL; 
   m_pf=NULL; 
  } 
  
  delegate(PFT pf) 
  { 
   operator=(pf); 
  } 
  
  template<typename OT> 
   delegate( 
   OT *pObject, 
   typename to_member_function_pointer<OT, PFT>::type pmf 
   ) 
  { 
   m_pObject=reinterpret_cast<object*>(pObject); 
   m_pmf=*(reinterpret_cast<object_member_function_pointer*>(&pmf)); 
  } 
  
  template<typename OT> 
   delegate( 
   OT &pObject, 
   typename to_member_function_pointer<OT, PFT>::type pmf 
   ) 
  { 
   m_pObject=reinterpret_cast<object*>(&pObject); 
   m_pmf=*(reinterpret_cast<object_member_function_pointer*>(&pmf)); 
  } 
  
  template<typename OT> 
   delegate( 
   const OT *pObject, 
   typename to_const_member_function_pointer<OT, PFT>::type pmf 
   ) 
  { 
   m_pObject=const_cast<object*>(reinterpret_cast<object*>(pObject)); 
   m_pmf=*(reinterpret_cast<object_member_function_pointer*>(&pmf)); 
  } 
  
  template<typename OT> 
   delegate( 
   const OT &pObject, 
   typename to_const_member_function_pointer<OT, PFT>::type pmf 
   ) 
  { 
   m_pObject=const_cast<object*>(reinterpret_cast<object*>(&pObject)); 
   m_pmf=*(reinterpret_cast<object_member_function_pointer*>(&pmf)); 
  } 
  
  delegate & operator=(PFT pf) 
  { 
   m_pf=pf; 
   m_pObject=0; 
   return *this; 
  } 
  template<int> 
:gcc的函數(shù)模板不許無參數(shù)，加了個(gè)占位的"int"才能通過 
   result_type operator()() 
  { 
   if(m_pObject) 
    return (m_pObject->*m_pmf)(); 
   else 
    return m_pf(); 
  } 
  template<typename AT> 
   result_type operator()( 
   AT a1 
   ) 
  { 
   if(m_pObject) 
    return (m_pObject->*m_pmf)(a1); 
   else 
    return m_pf(a1); 
  } 
  template<typename AT1, typename AT2> 
   result_type operator()( 
   AT1 a1, 
   AT2 a2 
   ) 

{ 
   if(m_pObject) 
    return (m_pObject->*m_pmf)(a1,a2); 
   else 
    return m_pf(a1,a2); 
  } 
  template<typename AT1, typename AT2, typename AT3> 
   result_type operator()( 
   AT1 a1, 
   AT2 a2, 
   AT3 a3 
   ) 
  { 
   if(m_pObject) 
    return (m_pObject->*m_pmf)(a1,a2,a3); 
   else 
    return m_pf(a1,a2,a3); 
  } 
}; 
int gf(int) 
{ 
 return 0; 
} 
class Test 
{ 
public: 
 int f(int){return 0;} 
}; 
typedef delegate < int (*)(int) > my_delegate; 
int main() 
{ 
 Test t;

 my_delegate d1=&gf; // 普通函數(shù)
 my_delegate d2=my_delegate(t,&Test::f); //對(duì)象和類成員函數(shù)
 d1(0); //調(diào)用
 d2(2); 
}