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  1. #include <iostream>
  2.  
  3. ///define a matrix class
  4. ///this is a large object that can hold big memory
  5. class matrix
  6. {
  7.         int rows;
  8.         int cols;
  9.         double **mat;
  10.  
  11.         public:
  12.  
  13.         matrix( )
  14.         {
  15.                 //default constructor
  16.                 rows = cols = 0;
  17.                 mat = 0;
  18.         };
  19.  
  20.         //constructor
  21.         matrix( int r, int c )
  22.         {
  23.                 std::cout << "ctor called\n";
  24.                 rows = r;
  25.                 cols = c;
  26.                 mat = new double* [ r ];
  27.                 for( int i = 0; i < r; ++i )
  28.                         mat[ i ] = new double [ c ];
  29.         };
  30.  
  31.         //copy constructor -- method for initializing one matrix directly from another
  32.         matrix( const matrix& other)
  33.         {
  34.                 std::cout << "copy ctor called\n";
  35.                 rows = other.rows;
  36.                 cols = other.cols;
  37.                 mat = new double* [rows];
  38.                 for( int i = 0; i < rows; ++i )
  39.                 {
  40.                         mat[i] = new double [ cols ];
  41.                         for( int j = 0; j < cols; ++j )
  42.                                 mat[i][j] = other.mat[i][j];
  43.                 }
  44.         };
  45.  
  46.         //destructor
  47.         ~matrix( )
  48.         {
  49.                 std::cout << "dtor called\n";
  50.                 for( int i = 0 ; i < rows; ++i )
  51.                         if( mat[i] ) delete [] mat[i];
  52.                 if( mat ) delete [] mat;
  53.                 mat = 0;
  54.         };
  55.  
  56.         ///overload operator +
  57.         matrix operator+( const matrix &other )
  58.         {
  59.                 std::cout << "op+ called\n";
  60.                 matrix m(other.rows, other.cols);
  61.                 for( int i = 0; i < other.rows; i++ )
  62.                         for( int j = 0; j < other.cols; j++ )
  63.                                 m.mat[i][j] = mat[i][j] + other.mat[i][j];
  64.                 return m;
  65.         };
  66.  
  67.         //get a matrix element
  68.         double &element(int i, int j) { return mat[i][j]; }
  69.  
  70. };
  71.  
  72.  
  73.  
  74. int main( )
  75. {
  76.         ///initialize matrices -- bug dense matrices
  77.         matrix M1(1000,1000), M2(1000,1000);
  78.  
  79.         for( int i = 0; i < 1000; ++i )
  80.         {
  81.                 for( int j = 0; j < 1000; ++j )
  82.                 {
  83.                         M1.element(i,j) = 1;
  84.                         M2.element(i,j) = 2;
  85.                 }
  86.         }
  87.  
  88.  
  89.         ///DO the following!
  90.         matrix M3 = M1 + M2;
  91.         std::cout << M3.element(500,500) << '\n';
  92. }
  93.  
Success #stdin #stdout 0.04s 2856KB
comments (?)
stdin 
Standard input is empty
stdout 
ctor called
ctor called
op+ called
ctor called
3
dtor called
dtor called
dtor called
https://ideone.com/fSDbU
language:
C++ (gcc 8.3)
created:
12 years ago
visibility:
public

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