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  1. #include <iostream>
  2.  
  3. template<typename T, size_t columns>
  4. class TransMatrix {
  5.   using Matrix = T(*)[columns];
  6.   class Column {
  7.    public:
  8.     const T& operator[](const size_t column_index) const {
  9.       return m_[column_index][line_index_];
  10.     }   
  11.  
  12.    private:
  13.     friend class TransMatrix;
  14.     Column(const Matrix P, size_t lines) : m_(P), lines_(lines) { } 
  15.     const Matrix m_; 
  16.     const size_t lines_;
  17.     size_t line_index_;
  18.   };  
  19.  
  20.  public:
  21.   TransMatrix(Matrix m, size_t lines) : column_(Column(m, lines)) { } 
  22.  
  23.   Column& operator[](const size_t line_index) {
  24.     column_.line_index_ = line_index;
  25.     return column_;
  26.   }
  27.  
  28.  private:
  29.   Column column_;
  30. };
  31.  
  32. int main(int argc, char* argv[]) {
  33.   constexpr int kColumns = 4;
  34.  
  35.   int a[3][kColumns] = { 
  36.     { 1, 2, 3, 4 },
  37.     { 5, 6, 7, 8 },
  38.     { 9, 10, 11, 12 }
  39.   };  
  40.  
  41.   TransMatrix<int, kColumns> trans(a, 3); 
  42.  
  43.   for (int i = 0; i < 4; i++) {
  44.     for(int j = 0; j < 3; j++) {
  45.       std::cout << trans[i][j] << ", ";
  46.     }   
  47.     std::cout << std::endl;
  48.   }
  49.  
  50.   std::cout << std::endl;
  51. }
Success #stdin #stdout 0s 3296KB
comments (?)
stdin 
Standard input is empty
stdout 
1, 5, 9, 
2, 6, 10, 
3, 7, 11, 
4, 8, 12,
https://ideone.com/yU0gd6
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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