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  1. #include <iostream>
  2. #include <string>
  3. #include <vector>
  4.  
  5. typedef std::vector<std::vector<double>> matrix_type;
  6.  
  7. template <typename T> // a handy template to output a vector with <<
  8. std::ostream &operator <<(std::ostream &out, const std::vector<T> &obj)
  9. {
  10.     out << "<";
  11.     const char *sep = "";
  12.     for (auto &item : obj) // for each item in the vector
  13.     {
  14.         out << sep << item;
  15.         sep = ", ";
  16.     }
  17.     return out << ">";
  18. }
  19.  
  20. int main()
  21. {
  22.     matrix_type identity = {{1, 0, 0}, {0, 1, 0}, {0, 0, 1}};
  23.     std::cout << "identity = " << identity << "\n\n";
  24.  
  25.     matrix_type copy1(identity); // deep copy using constructor
  26.     copy1[0][2] = 42;
  27.     std::cout << "copy1 = " << copy1 << "\n";
  28.     std::cout << "identity = " << identity << "\n\n";
  29.  
  30.     matrix_type copy2;
  31.     copy2 = identity;   // deep copy using assignment operator
  32.     copy2[1][0] = 24;
  33.     std::cout << "copy2 = " << copy2 << "\n";
  34.     std::cout << "copy1 = " << copy1 << "\n";
  35.     std::cout << "identity = " << identity << "\n\n";
  36.  
  37.     return 0;
  38. }
  39.  
Success #stdin #stdout 0s 4524KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
identity = <<1, 0, 0>, <0, 1, 0>, <0, 0, 1>>

copy1 = <<1, 0, 42>, <0, 1, 0>, <0, 0, 1>>
identity = <<1, 0, 0>, <0, 1, 0>, <0, 0, 1>>

copy2 = <<1, 0, 0>, <24, 1, 0>, <0, 0, 1>>
copy1 = <<1, 0, 42>, <0, 1, 0>, <0, 0, 1>>
identity = <<1, 0, 0>, <0, 1, 0>, <0, 0, 1>>
https://ideone.com/YFN29w
Demo of "deep copy" of nested vectors. Also a sample of overloading << operator to display vectors.
language:
C++14 (gcc 8.3)
created:
6 years ago
visibility:
public

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