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  1. #include <iostream>
  2. #include <functional>
  3. #include <sstream>
  4. #include <vector>
  5. using namespace std;
  6.  
  7. int f1(int x) {
  8.   return x;
  9. }
  10.  
  11. string f2(int x) {
  12.   return std::to_string(x);
  13. }
  14.  
  15. long long f3(int x) {
  16.   return x;
  17. }
  18.  
  19. template<class T>
  20. function<string(int)> conv(function<T(int)> f) {
  21.     return [&](int x) -> string {
  22.         stringstream ss;
  23.         ss << f(x);
  24.         return ss.str();
  25.     };
  26. }
  27.  
  28. template<class T>
  29. function<string(int)> conv1(T(*f)(int)) {
  30.     return [f](int x) -> string {
  31.         stringstream ss;
  32. 	    std::function<T(int)> _f(f);
  33.         ss << _f(x);
  34.         return ss.str();
  35.     };
  36. }
  37.  
  38. int main() {
  39.  
  40.     vector<function<string(int)>> funcs = {
  41.       conv(std::function<int(int)>(f1)),
  42.       conv1(f1),
  43.       conv(std::function<string(int)>(f2)),
  44.       conv1(f2),
  45.       conv(std::function<long long(int)>(f3)),
  46.       conv1(f3),
  47.     };
  48.     std::cout << "int(int) " << funcs[0](12) << " " << funcs[1](13) << std::endl;
  49.     std::cout << "string(int) "<< funcs[2](12) << " " << funcs[3](13) << std::endl;
  50.     std::cout << "long long(int) "<< funcs[4](12) << " " << funcs[5](13) << std::endl;
  51.     return 0;
  52. }
  53.  
Success #stdin #stdout 0s 15240KB
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stdin
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Standard input is empty
stdout
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int(int) 12 13
string(int) 12 13
long long(int) 12 13
https://ideone.com/ZSK5Yc
language:
C++14 (clang 8.0)
created:
8 years ago
visibility:
public

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