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  1. #include <memory>
  2. #include <utility>
  3.  
  4. template <typename T>
  5. struct function;
  6.  
  7. template <typename R, typename... A>
  8. struct function<R(A...)> {
  9.     struct inner_fun_base {
  10.         virtual R call(A...) = 0;
  11.     };
  12.  
  13.     template <typename F>
  14.     struct inner_fun : inner_fun_base {
  15.         inner_fun(F f) : f(f) {}
  16.         F f;
  17.         virtual R call(A... a) {
  18.             return f(std::forward<A>(a)...);
  19.         }
  20.     };
  21.  
  22.     std::unique_ptr<inner_fun_base> ptr;
  23.  
  24.     template <typename F>
  25.     function(F f) // I'm going by value here for simplicity
  26.     :ptr(new inner_fun<F>(f)) {}
  27.  
  28.     R operator()(A... a) {
  29.         return ptr->call(std::forward<A>(a)...);
  30.     }
  31. };
  32.  
  33. #include <iostream>
  34.  
  35. int main() {
  36.     function<bool(int)> f([](int n) { return n > 3; });
  37.     std::cout << f(2) << f(4);
  38. }
  39.  
Success #stdin #stdout 0s 3016KB
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01
https://ideone.com/yU5cW
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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