overload
CodeGuru Home VC++ / MFC / C++ .NET / C# Visual Basic VB Forums Developer.com
Results 1 to 12 of 12

Thread: overload

  1. #1
    Join Date
    Dec 2010
    Posts
    16

    overload

    the operator+ and operator^ are not working. Can anyone correct?.

    Code:
    #include <iostream>
    #include <algorithm>
    
    using namespace std;
    
    template <class T>
    class Array2D
    {
        T* data;
        int w, h;
    public:
        Array2D(int X, int Y) : w(X), h(Y)
        {
            data = new T[w*h];
        }
       
        ~Array2D()
        {
            if (data != NULL)
            {
                delete [] data;
                data = NULL;
            }
        }
       
        T& operator ()(int Col, int Row)
        {
            return data[Row*w+Col];
        }
       
        Array2D operator+( Array2D& m)
        {
            int w = m.width();
            int h = m.height();
            Array2D theArray2D(w,h);
            for (int r=0;r<h;r++)
            {
                for (int c=0;c<w;c++)
                {
                    theArray2D(c,r)=data[c*w+r]+m(c,r);
                }
            }
            return theArray2D;
        }
    
        Array2D operator^( cont T& t)
        {
          //need to be filled
        }
    
        int width() 
        {return w;}
       
        int height() 
        {return h;}
    
    };
    
    int main( )
    {
        int c = 5;
        int r = 6;
    
        Array2D<int> b(c,r);
        Array2D<int> b1(c,r);
    
        for(int j=0; j<r; j++)
        {
            for(int i=0; i<c; i++)
            {
                b(i,j) = i+j;
    	    b1(i,j) = i+j;
            }
        }
    
        Array2D<int> a1 = b + b1;
        Array2D<int> a2 = b ^ 2;
    
        for(int j=0; j<r; j++)
        {
            for(int i=0; i<c; i++)
            {
                std::cout << a1(i,j) << "\t";
            }
            std::cout << "\n";
        }
    
        return 0;
    }

  2. #2
    Join Date
    Apr 1999
    Posts
    27,424

    Re: overload

    Quote Originally Posted by CHO View Post
    the operator+ and operator^ are not working. Can anyone correct?.
    What do you mean by "not working"?

    Secondly, for what reason are you overloading operator ^? If you're overloading it to do powers -- forget it. The "^" precedence level is incompatible with it being used for power operations.

    Regards,

    Paul McKenzie

  3. #3
    Join Date
    Dec 2010
    Posts
    16

    Re: overload

    these are the results from a1(i,j) , operator+.:

    -572662307 1 0 0 -33686019
    -572662307 524295 786688 3233816 0
    273774084 177 8 2 134
    -33686019 3232304 3232360 -33686019 -572662307
    458778 -572719104 3211848 3211848 -572662307
    -572662307 -572662307 -572662307 -572662307 -572662307

    How do i overload power?.

  4. #4
    Join Date
    Apr 1999
    Posts
    27,424

    Re: overload

    Quote Originally Posted by CHO View Post
    these are the results from a1(i,j) , operator+.:

    -572662307 1 0 0 -33686019
    -572662307 524295 786688 3233816 0
    273774084 177 8 2 134
    -33686019 3232304 3232360 -33686019 -572662307
    458778 -572719104 3211848 3211848 -572662307
    -572662307 -572662307 -572662307 -572662307 -572662307
    Before asking one of us to debug your code, have you debugged your code? Every programmer makes mistakes, and debugging your own code is part and parcel of learning how to program.
    How do i overload power?.
    You don't. You write a function to do it.

    Notice that C++ has a pow() function, and does not use ^ for powers for the reasons I described.

    Regards,

    Paul McKenzie

  5. #5
    Join Date
    Dec 2010
    Posts
    16

    Re: overload

    made it working!!!!

  6. #6
    Join Date
    Dec 2010
    Posts
    16

    Re: overload

    value of b1 changes after the + operation. Tried to prevent that , but no luck.

    Code:
    #include <iostream>
    #include <algorithm>
    
    using namespace std;
    
    template <class T>
    class Array2D
    {
        T* data;
        int w, h;
    public:
        Array2D(int X, int Y) : w(X), h(Y)
        {
            data = new T[w*h];
        }
       
        ~Array2D()
        {
            if (data != NULL)
            {
                delete [] data;
                data = NULL;
            }
        }
       
        T& operator ()(int Col, int Row)
        {
            return data[Row*w+Col];
        }
       
        Array2D<T>& operator+( Array2D<T>& m)
        {
    		//Array2D<int> c(w,h);
    
    		//Array2D<int>& result = c; 
    
    	Array2D& result = m;
            for (int r=0;r<h;r++)
            {
                for (int c=0;c<w;c++)
    			{
    				result(c,r) = (*this)(c,r)+m(c,r);
    			}
    		}
    		return result;
        }
    
        int width() 
        {return w;}
       
        int height() 
        {return h;}
    
    };
    
    int main( )
    {
        int c = 5;
        int r = 6;
    
        Array2D<int> b(c,r);
        Array2D<int> b1(c,r);
    
        for(int j=0; j<r; j++)
        {
            for(int i=0; i<c; i++)
            {
                b(i,j) = 2;
    	    b1(i,j) = 1;
            }
        }
    
        //value of b1 changes after this line. Tried to prevent that , but no luck.
        Array2D<int>& a1 = b + b1; 
    
        for(int j=0; j<r; j++)
        {
            for(int i=0; i<c; i++)
            {
                std::cout << a1(i,j) << "\t";
            }
            std::cout << "\n";
        }
    
        return 0;
    }

  7. #7
    Join Date
    Dec 2010
    Posts
    16

    Re: overload

    made a change:
    Code:
        Array2D<T>& operator+( Array2D<T>& m)
        {
    		Array2D<int> *n = new Array2D<int>(w,h);
    
    		Array2D<int>& result = *n;
            for (int r=0;r<h;r++)
            {
                for (int c=0;c<w;c++)
    			{
    				result(c,r) = (*this)(c,r)+m(c,r);
    			}
    		}
    		return result;
        }
    it works now. if there is a better way to do this, let me know.

  8. #8
    Join Date
    Aug 2000
    Location
    West Virginia
    Posts
    7,564

    Re: overload

    1. I see a "new" , but no delete. You will have a memory leak

    2. You do memory allocation. You will need to code up a proper
    copy constructor and assignment operator

    3. Normally, you do not make operator + a member variable.
    You make operator += a member (returning a reference to *this

    4. You make operator + a non member function, coded in terms
    of operator += and the copy constructor.

  9. #9
    Join Date
    Dec 2010
    Posts
    16

    Re: overload

    I am new to operator overloading. If anyone can make the changes to the class and the main(), to see, it be useful.

  10. #10
    Join Date
    Aug 2000
    Location
    West Virginia
    Posts
    7,564

    Re: overload

    Here is an example (non templated ... "1D" array).

    I did not check everything ... but this will give you an idea ...

    Code:
    #include <iostream>
    #include <algorithm>
    
    using namespace std;
    
    class Array
    {    
      int * pArray;
      
      int size;
      
    public:
        
      Array(int dim = 10) : size(dim) 
      {
        pArray = new int [size];
      }
      
      Array (const Array & rhs)
      {
        pArray = new int [rhs.size];
        size = rhs.size;
        
        for (int i=0; i<size; ++i)
        {
          pArray[i] = rhs.pArray[i];
        }
      }
      
      void Swap (Array & rhs) throw ()
      {
        std::swap(size,rhs.size);
        std::swap(pArray,rhs.pArray);
      }
      
      Array & operator = (const Array & rhs)
      {
         Array temp(rhs);
         Swap(temp);
         return *this;
      }
      
      Array & operator += (const Array & rhs)
      {
        if (size > rhs.size)
        {
          // you need to decide what to do here
        }
        else
        {
          for (int i=0; i<size; ++i)
          {
    	pArray[i] += rhs.pArray[i];
          }
        }
        
        return *this;
      }
      
      size_t Size() { return size; }
      
      const int & operator [] (int i) const
      {
        return pArray[i];
      }
      
      int & operator [] (int i)
      {
        return pArray[i];
      }
      
      ~Array()
      {
        delete [] pArray;
      }
    };
    
    Array operator + (const Array & lhs , const Array & rhs)
    {
      Array temp(lhs);
      return temp += rhs;
    }
    
    int main()
    {
      Array a(3);
      Array b(3);
      Array c(3);
      
      for (int i=0; i<a.Size(); ++i)
      {
        a[i] = 1;
        b[i] = 6;
      }
      
      c = a + b;
      
      for (int i=0; i<c.Size(); ++i)
      {
        cout << c[i] << "\n";
      }
      
      return 0;
    }
    Last edited by Philip Nicoletti; December 30th, 2010 at 01:34 PM.

  11. #11
    Join Date
    Apr 2008
    Posts
    726

    Re: overload

    Quote Originally Posted by CHO View Post
    made a change:
    Code:
        Array2D<T>& operator+( Array2D<T>& m)
        {
    		Array2D<int> *n = new Array2D<int>(w,h);
    
    		Array2D<int>& result = *n;
            for (int r=0;r<h;r++)
            {
                for (int c=0;c<w;c++)
    			{
    				result(c,r) = (*this)(c,r)+m(c,r);
    			}
    		}
    		return result;
        }
    it works now. if there is a better way to do this, let me know.
    operator+ should not change either argument, therefore it should return an object that is neither of the arguments i.e. it should not return a reference, but a new object, like philip has shown.

  12. #12
    Join Date
    Nov 2006
    Location
    Essen, Germany
    Posts
    1,344

    Re: overload

    1) You can eliminate the necessity of a copy constructor/assignment operator by using std::vector instead of a C-style array.

    2) binary operators (i.e. operator+) should be implemented as non-member functions.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  


Azure Activities Information Page

Windows Mobile Development Center


Click Here to Expand Forum to Full Width

This is a CodeGuru survey question.


Featured


HTML5 Development Center