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  1. #include <iostream>
  2. #include <memory>
  3. #include <type_traits>
  4.  
  5. template <class F>
  6. struct Decomposer;
  7.  
  8. template <class R, class A>
  9. struct Decomposer<R (A)>
  10. {
  11.   typedef R return_type;
  12.   typedef A argument_type;
  13. };
  14.  
  15.  
  16. template <class F>
  17. struct my_function
  18. {
  19.   typedef typename Decomposer<F>::return_type return_type;
  20.   typedef typename Decomposer<F>::argument_type argument_type;
  21.  
  22.   return_type operator() (argument_type arg) const {
  23.   	return (*impl)(arg);
  24.   }
  25.  
  26.   template <class From>
  27.   my_function(From &&from)
  28.   {
  29.   	struct ConcreteImpl : Impl
  30.   	{
  31.   		typename std::remove_reference<From>::type functor;
  32.   		ConcreteImpl(From &&functor) : functor(std::forward<From>(functor)) {}
  33.   		virtual return_type operator() (argument_type arg) const override
  34.   		{
  35.   			return functor(arg);
  36.   		}
  37.   	};
  38.   	impl.reset(new ConcreteImpl(std::forward<From>(from)));
  39.   }
  40.  
  41. private:
  42.   struct Impl {
  43.   	virtual ~Impl() {}
  44.   	virtual return_type operator() (argument_type arg) const = 0;
  45.   };
  46.  
  47.   std::unique_ptr<Impl> impl;
  48. };
  49.  
  50.  
  51. int main(int argc, char* argv[])
  52. {
  53.     int mybool = 5;
  54.  
  55.     auto foo = [&] (int arg) {
  56.         return mybool * arg;
  57.     };
  58.  
  59.     my_function<int(int)> foo2 = foo;
  60.  
  61.     int result = foo2(42);
  62.  
  63.     std::cout << result << std::endl;
  64.  
  65.     return 0;
  66. }
Success #stdin #stdout 0s 3472KB
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https://ideone.com/iCJ05b
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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