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  1. #include <iostream>
  2. #include <functional>
  3.  
  4. template <typename> class curry;
  5.  
  6. template <typename _Res>
  7. class curry< _Res() >
  8. {
  9. public:
  10.     typedef std::function< _Res() > _Fun;
  11.     typedef _Res _Ret;
  12.  
  13. private:
  14.     _Fun _fun;
  15.  
  16. public:
  17.     explicit curry (_Fun fun)
  18.         : _fun(fun) { }
  19.  
  20.     operator _Ret ()
  21.     { return _fun(); }
  22. };
  23.  
  24. template <typename>
  25. class decurry;
  26.  
  27. template <typename _Res, typename _Arg, typename... _Args>
  28. class curry< _Res(_Arg, _Args...) >
  29. {
  30. public:
  31.     typedef std::function< _Res(_Arg, _Args...) > _Fun;
  32.     typedef curry< _Res(_Args...) > _Ret;
  33.  
  34. private:
  35.     class apply
  36.     {
  37.     private:
  38.         _Fun _fun;
  39.         _Arg _arg;
  40.  
  41.     public:
  42.         apply (_Fun fun, _Arg arg)
  43.             : _fun(fun), _arg(arg) { }
  44.  
  45.         _Res operator() (_Args... args)
  46.         { return _fun(_arg, args...); }
  47.     };
  48.  
  49. private:
  50.     _Fun _fun;
  51.  
  52. public:
  53.     explicit curry (_Fun fun)
  54.         : _fun(fun) { }
  55.  
  56.     _Ret operator() (_Arg arg)
  57.     { return _Ret(apply(_fun, arg)); }
  58.  
  59.  
  60.     friend class decurry< curry<_Res(_Arg, _Args...)> >;
  61. };
  62.  
  63. template <typename>
  64. class decurry;
  65.  
  66. template <typename _Res, typename... _Args>
  67. class decurry< curry<_Res(_Args...)> > {
  68. public:
  69.     typedef curry<_Res(_Args...)> _Curried;
  70.     typedef typename curry<_Res(_Args...)>::_Fun _Raw;
  71.  
  72.     decurry(_Curried fn): _fn(fn) {}
  73.  
  74.     _Res operator() (_Args... rest) {
  75.         return _fn._fun(rest...);
  76.     }
  77. private:
  78.     _Curried _fn;
  79. };
  80.  
  81. template <typename _Res, typename _Res2, typename... _Args2, typename... _Args>
  82. class curry< _Res(_Res2(_Args2...), _Args...) >
  83. {
  84. public:
  85.     typedef curry< _Res2(_Args2...) > _Arg;
  86.     typedef std::function< _Res2(_Args2...) > _RawFun;
  87.     typedef std::function< _Res(_RawFun, _Args...) > _Fun;
  88.     typedef curry< _Res(_Args...) > _Ret;
  89.  
  90. private:
  91.     class apply
  92.     {
  93.     private:
  94.         _Fun _fun;
  95.         _RawFun _arg;
  96.  
  97.     public:
  98.         apply (_Fun fun, _RawFun arg)
  99.             : _fun(fun), _arg(arg) { }
  100.  
  101.         _Res operator() (_Args... args)
  102.         { return _fun(_arg, args...); }
  103.     };
  104.  
  105. private:
  106.     _Fun _fun;
  107.  
  108. public:
  109.     explicit curry (_Fun fun)
  110.         : _fun(fun) { }
  111.  
  112.     _Ret operator() (_Arg arg)
  113.     { return _Ret(apply(_fun, decurry<_Arg>(arg))); }
  114. };
  115.  
  116. int test(std::function<int(int,int)> f, int x)
  117. { return f(3, 4) * x; }
  118.  
  119. int main ()
  120. {
  121.     auto func_xy = curry<int(int(int,int),int)>(test);
  122.     auto plus_xy = curry<int(int,int)>(std::plus<int>());
  123.     auto func_px = func_xy(plus_xy);
  124.     auto func_p5 = func_px(5);
  125.     std::cout << func_p5 << std::endl;
  126.  
  127.     return 0;
  128. }
  129.  
Success #stdin #stdout 0s 2968KB
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https://ideone.com/bTJAL
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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