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  1. #include <cstring>
  2. #include <iostream>
  3.  
  4. using std::size_t;
  5.  
  6. class Mesh2D
  7. {
  8. private:
  9.  
  10.     double* mesh;
  11.     size_t  rows;
  12.     size_t  columns;
  13.  
  14. public:
  15.  
  16.     /* constructor */
  17.     Mesh2D(size_t Nx, size_t Ny){
  18.         rows    = Nx;
  19.         columns = Ny;
  20.         mesh    = new double[Nx*Ny] {};
  21.         std::cout << "Mesh created." << std::endl;
  22.     }
  23.  
  24.     /* destructor */
  25.     ~Mesh2D()
  26.     {
  27.         delete[] mesh;
  28.         std::cout << "Mesh deleted." << std::endl;
  29.     }
  30.  
  31.     /* accessors */
  32.     double getrows() const {return rows;}
  33.     double getcolumns() const {return columns;}
  34.     double& operator()(size_t i, size_t j)
  35.     {
  36.         if (i > rows || j > columns){
  37.             throw std::out_of_range("Index exceeds array bounds.");
  38.         }
  39.         return mesh[j + i*columns]; // row major access
  40.     }
  41.  
  42. 	double operator()(size_t i, size_t j) const
  43.     {
  44.         if (i > rows || j > columns){
  45.             throw std::out_of_range("Index exceeds array bounds.");
  46.         }
  47.         return mesh[j + i*columns]; // row major access
  48.     }
  49.  
  50.     /* copy constructor */
  51.     Mesh2D& operator=(const Mesh2D& rhs) // what is the difference between this line and the following? inline operator=(const Mesh2D& rhs)
  52.     {
  53.         if (rhs.rows != rows || rhs.columns != columns){
  54.             throw std::out_of_range("Assignment cannot be performed, mesh dimensions do not agree.");
  55.         }
  56.         if (&rhs == this) //copying the same object
  57.         	return *this;
  58.  
  59. //        I want to avoid using a for loop
  60. //        for (int i=0; i<rows*columns; i++){
  61. //            mesh[i] = rhs.mesh[i];
  62. //        }
  63. //      Use this instead
  64.         std::memcpy(mesh, rhs.mesh, rows*columns * sizeof(double)); //however the output is not the expected.
  65.         std::cout << "copied!" << std::endl;
  66.         return *this;
  67.     }
  68.  
  69. };
  70.  
  71.  
  72.  
  73. void PrintMesh2D(const Mesh2D &mesh){ //why isn't it going to work if I add const? I mean: void PrintMesh2D(const Mesh2D &mesh)
  74.  
  75.     for (int i=0; i<mesh.getrows(); i++){
  76.  
  77.         for (int j=0; j<mesh.getcolumns(); j++){
  78.  
  79.             std::cout << mesh(i,j) << " ";
  80.         }
  81.         std::cout << std::endl;
  82.     }
  83. }
  84.  
  85. int main()
  86. {
  87.  
  88.     Mesh2D mesh{3,3};
  89.     Mesh2D newmesh{3,3};
  90.  
  91.     for (int i=0; i<mesh.getrows(); i++){
  92.         for (int j=0; j<mesh.getcolumns(); j++){
  93.             mesh(i,j) = j + i * mesh.getcolumns();
  94.         }
  95.     }
  96.  
  97.     newmesh = mesh;
  98.     PrintMesh2D(newmesh);
  99.  
  100. }
Success #stdin #stdout 0s 4452KB
comments (?)
stdin
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Standard input is empty
stdout
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Mesh created.
Mesh created.
copied!
0 1 2 
3 4 5 
6 7 8 
Mesh deleted.
Mesh deleted.
https://ideone.com/seOSwN
language:
C++14 (clang 8.0)
created:
5 years ago
visibility:
public

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