Re: Can we override [][] ?

"Jim Langston" <>
Tue, 30 May 2006 17:56:34 -0700
"Mike Wahler" <> wrote in message

"Jim Langston" <> wrote in message

I wanted to do an operator override for [][] but couldnt' figure out the
syntax. I tried this (code that doesn't compile commented out with //:

class CMyBitmap
   CMyBitmap( int Rows, int Columns ): Rows_( Rows ), Columns_( Columns )
       Data_ = new SPixel[ Rows * Columns ];
       delete[] Data_;

// error C2804: binary 'operator [' has too many parameters
// SPixel& operator[]( const int Row, const int Column )
// {
// return Data_[ Columns_ * Row + Column ];
// }

// error C2092: '[]' array element type cannot be function
// SPixel& operator[][]( const int Row, const int Column )

   SPixel& Pixel( const int Row, const int Column )
       return Data_[ Columns_ * Row + Column ];

   SPixel* Data_;
   int Rows_;
   int Columns_;

   // No copy or assignment yet so disable by making private.
   CMyBitmap ( CMyBitmap const& ) {};
   CMyBitmap& operator=( CMyBitmap const& ) {};


Can we override 2d array access?

Certainly. But...
[][] is not an operator, it's two instances of the single
operator []. If you have your operator[] do the 'right
thing', you shouldn't have any problems using expressions
such as x[], x[][], x[][][], etc. Post back if you need
more help or an example.

I had goggled for operator[] but goggle doesn't seem to index special
characters (such as '[') so the hits weren't very orderly and it took me a
long time to even find the syntax for [] My manual didn't give me any
examples, time to get a new manual.

I would need an example please, as I don't know how to override[] to accept
two paramters but you seem to indicate it is two instances of []. What is
the 'right thing' or can you direct me to a web page on the subject? As I
said, in this case Google was not my friend.

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