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  1. #include <type_traits>
  2. #include <functional>
  3. #include <algorithm>
  4. #include <stdexcept>
  5. #include <iostream>
  6. #include <typeinfo>
  7. #include <utility>
  8. #include <ostream>
  9. #include <vector>
  10. #include <string>
  11.  
  12. using namespace std;
  13.  
  14. // _____________________________Implementation__________________________________________
  15.  
  16. #define USE_VARIADIC_TEMPLATES 0
  17.  
  18. template<typename Callback,typename Function>
  19. bool func_compare(const Function &lhs,const Function &rhs)
  20. {
  21.     typedef typename conditional<is_function<Callback>::value,typename add_pointer<Callback>::type,Callback>::type request_type;
  22.     if (const request_type* lhs_internal = lhs.template target<request_type>())
  23.         if (const request_type* rhs_internal = rhs.template target<request_type>())
  24.             return *rhs_internal == *lhs_internal;
  25.     return false;
  26. }
  27.  
  28. #if USE_VARIADIC_TEMPLATES
  29.     #define FUNC_SIG_TYPES typename ...Args
  30.     #define FUNC_SIG_TYPES_PASS Args...
  31. #else
  32.     #define FUNC_SIG_TYPES typename function_signature
  33.     #define FUNC_SIG_TYPES_PASS function_signature
  34. #endif
  35.  
  36. template<FUNC_SIG_TYPES>
  37. struct function_comparable: function<FUNC_SIG_TYPES_PASS>
  38. {
  39.     typedef function<FUNC_SIG_TYPES_PASS> Function;
  40.     bool (*type_holder)(const Function &,const Function &);
  41. public:
  42.     function_comparable(){}
  43.     template<typename Func>
  44.     function_comparable(Func f_)
  45.         : Function(f_), type_holder(func_compare<Func,Function>)
  46.     {
  47.     }
  48.     template<typename Func>
  49.     function_comparable &operator=(Func f_)
  50.     {
  51.         Function::operator=(f_);
  52.         type_holder=func_compare<Func,Function>;
  53.         return *this;
  54.     }
  55.     friend bool operator==(const Function &lhs,const function_comparable &rhs)
  56.     {
  57.         return rhs.type_holder(lhs,rhs);
  58.     }
  59.     friend bool operator==(const function_comparable &lhs,const Function &rhs)
  60.     {
  61.         return rhs==lhs;
  62.     }
  63.     friend void swap(function_comparable &lhs,function_comparable &rhs)// noexcept
  64.     {
  65.         lhs.swap(rhs);
  66.         lhs.type_holder.swap(rhs.type_holder);
  67.     }
  68. };
  69.  
  70. // ________________________________Example______________________________________________
  71.  
  72. typedef void (function_signature)();
  73.  
  74. void func1()
  75. {
  76.     cout << "func1" << endl;
  77. }
  78.  
  79. void func3()
  80. {
  81.     cout << "func3" << endl;
  82. }
  83.  
  84. class func2
  85. {
  86.     int data;
  87. public:
  88.     explicit func2(int n) : data(n) {}
  89.     friend bool operator==(const func2 &lhs,const func2 &rhs)
  90.     {
  91.         return lhs.data==rhs.data;
  92.     }
  93.     void operator()()
  94.     {
  95.         cout << "func2, data=" << data << endl;
  96.     }
  97. };
  98. struct Caller
  99. {
  100.     template<typename Func>
  101.     void operator()(Func f)
  102.     {
  103.         f();
  104.     }
  105. };
  106. class Callbacks
  107. {
  108.     vector<function<function_signature>> v;
  109. public:
  110.     void register_callback_comparator(function_comparable<function_signature> callback)
  111.     {
  112.         v.push_back(callback);
  113.     }
  114.     void register_callback(function<function_signature> callback)
  115.     {
  116.         v.push_back(callback);
  117.     }
  118.     void unregister_callback(function_comparable<function_signature> callback)
  119.     {
  120.         auto it=find(v.begin(),v.end(),callback);
  121.         if(it!=v.end())
  122.             v.erase(it);
  123.         else
  124.             throw runtime_error("not found");
  125.     }
  126.     void call_all()
  127.     {
  128.         for_each(v.begin(),v.end(),Caller());
  129.         cout << string(16,'_') << endl;
  130.     }
  131. };
  132.  
  133. int main()
  134. {
  135.     Callbacks cb;
  136.     function_comparable<function_signature> f;
  137.     f=func1;
  138.     cb.register_callback_comparator(f);
  139.  
  140.     cb.register_callback(func2(1));
  141.     cb.register_callback(func2(2));
  142.     cb.register_callback(func3);
  143.     cb.call_all();
  144.  
  145.     cb.unregister_callback(func2(2));
  146.     cb.call_all();
  147.     cb.unregister_callback(func1);
  148.     cb.call_all();
  149. }
  150.  
Success #stdin #stdout 0s 3068KB
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stdin
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Standard input is empty
stdout
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func1
func2, data=1
func2, data=2
func3
________________
func1
func2, data=1
func3
________________
func2, data=1
func3
________________
https://ideone.com/sclqx2
language:
C++14 (gcc 8.3)
created:
12 years ago
visibility:
secret

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