c++ copy constructor, after copy random value -

i have errors copy constructor cant figure out, main question @ moment brought out in test programs comments. why second print out big number, , not three? thank in advance help.

template<class t> class array {     private:         t *cont;         unsigned int size;      public:      array()=default;       t& elementat(unsigned int i)     {     return cont[i];      }       array( const array &a )      {     cont = new int[ size ];      ( int = 0; < size; i++ )         cont[ ] = a.cont[ ];     }       array& operator = (const array& a)     {     int i,min_size;     if(size < a.size)         min_size = size;     else         min_size = a.size;     for(i=0; i<min_size; i++)         cont[i] = a.cont[i];     return (*this);     }       void addelement(t element) {         t *new_cont = new t[size + 1], *old_cont = cont;          (int = 0; < size; i++) {             new_cont[i] = old_cont[i];         }          new_cont[size] = element;         size++;          cont = new_cont;         delete old_cont;     }       unsigned int getsize() const     {     return size;     }       ~array()     {     delete [] cont;     }    }; 

and part of test program:

array<int> numbers;                  numbers.addelement (5);              numbers.addelement (11);             numbers.addelement (3);         cout << numbers.getsize()<<endl;  // here output: 3     cout<< numbers.elementat(1)<<endl; // output: 11         myarray<int> copy2;     copy2 = numbers;             cout << copy2.getsize()<<endl;  //  why output: 2686697, in here? why isn' t 3.     cout<< copy2.elementat(1)<<endl; // output: 11 

you using wrong size allocate memory in copy constructor.

array( const array &a )  {   // size copy first. without it, size unitialized   // value, lead undefined behavior.   size = a.size;   cont = new int[ size ];    ( int = 0; < size; i++ )     cont[ ] = a.cont[ ]; } 

the other problem see implementation of default constructor. default constructor can used in 2 ways:

array<int> numbers; 

or

array<int> numbers = array<int>(); 

the former result in uninitialized data while latter result in initialized data implementation. see details here.

you can change default constructor to:

array() : size(0), cont(null) {} 

to make code work identically in either way of constructing object.

the third problem operator= function. not perform true assignment. stores minimum number of elements 2 objects. try this:

   array& operator = (const array& a)    {       // make statements 'a = a;' noop.       if ( != &a )       {          // if size of lhs larger or equal size          // of rhs, lhs has enough memory store data          // rhs.          if ( this->size >= a.size )          {             this->size = a.size;             for(int i=0; i<a.size; i++)                cont[i] = a.cont[i];          }          else          {             // size of lhs smaller size of rhs,             // not have enough memory store data             // rhs. dellocate old memory. allocate new memory.             // copy data.             this->size = a.size;             delete [] cont;             cont = new int[this->size];             for(int i=0; i<a.size; i++)                cont[i] = a.cont[i];           }       }       return (*this);    }