Re: Overloading Operator[] through 'this' pointer?

From:
Immortal Nephi <Immortal_Nephi@hotmail.com>
Newsgroups:
comp.lang.c++
Date:
Tue, 8 Jun 2010 08:23:49 -0700 (PDT)
Message-ID:
<90a35a30-5aca-482c-8660-e2d05cc5460f@s9g2000yqd.googlegroups.com>
On Jun 7, 3:01 pm, Paul Bibbings <paul.bibbi...@gmail.com> wrote:

Immortal Nephi <Immortal_Ne...@hotmail.com> writes:

   Can overloading operator[] be connected to any member functions
through =91this' pointer? I do not want to insert assignment betwe=

en

array object and integer value. I prefer to place integer value in
the member function's parameter.

For example:

class Array
{
public:
   Array( int size ) : pData( new unsigned char[ size ] )
   {}

   ~Array()
   {
           delete [] pData;
   }

   int &operator[]( int index )
   {
           return pData[ index ];
   }

   Array &Set_LowNibble( unsigned char val, int index )
   {
           pData[ index ] &= 0xF0;
           pData[ index ] |= (val & 0x0F );
           return *this;
   }

   Array &Set_HighNibble( unsigned char val, int index )
   {
           pData[ index ] &= 0x0F;

           unsigned char temp = val;
           temp &= 0x0F;
           temp <<= 4;

           pData[ index ] |= temp;

           return *this;
   }

private:
   unsigned char *pData;
};

int main()
{
   Array array( 4 );

   array[ 0 ] = 0x1E; // Always valid code

   // Not valid code but you find another way
   array[ 1 ].Set_LowNibble( 0x0D, 1 ).Set_HighNibble( 0x02, 1 );

   return 0;
}


The following is just an idea to think about. I have not given very
much consideration to the details and I am not completely sure why you
are wanting it to work in this way.

   class Byte
   {
   public:
      Byte(unsigned char& c) : c_(c) { }
      Byte& operator=(unsigned char val)
      {
         c_ = val;
         return *this;
      }
      Byte& Set_LowNibble(unsigned char val)
      {
         c_ &= 0xF0;
         c_ |= (val & 0x0F);
         return *this;
      }
      Byte& Set_HighNibble(unsigned char val)
      {
         c_ &= 0x0F;
         unsigned char temp = val;
         temp &= 0x0F;
         temp <<= 4;
         c_ |= temp;
         return *this;
      }
      operator unsigned char&() { return c_; }
   private:
      unsigned char& c_;
   };

   class Array
   {
   public:
      Array(int size)
         : pData(new unsigned char[size])
      { }
      ~Array()
      {
         delete [] pData;
      }
      Byte operator[](int index)
      {
         return pData[index];
      }
   private:
      unsigned char *pData;
   };

   int main()
   {
      Array array(4);

      array[0] = 0x3C;

      array[1].Set_LowNibble(0x0D).Set_HighNibble(0x02);

      std::cout << array[0] << '\n';
      std::cout << array[1] << '\n';

      unsigned char& c_ref = array[1];
      c_ref = array[0];

      std::cout << array[0] << '\n';
      std::cout << array[1] << '\n';

      return 0;
   }

   /**
    * Output:
    * <
    * -
    * <
    * <
    */

    
That code looks great. One problem=97If I want to create a pointer,
Set_LowNibble and Set_HighNibble are not members of that class.

Array *pArray = new Array( 4 );

    What is another way to fix?

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