Re: operator[][][]

From: (Carl Barron)
Thu, 27 Jul 2006 14:52:46 GMT
In article <9wMxg.11890$>, Frederick Gotham
<> wrote:

kanze posted:

On the other hand, both C and C++ already have a syntax
for indexing "multiple dimension arrays": [i][j][k]. If at all
possible, a solution should be found which preserves this

(I still haven't quite formulated this in my mind yet, so I might have a
little difficulty in wording this...)

template <class T,size_t cols,size_t rows>
class Matrix
   T data[rows*cols];
   struct subscript_proxy
      T *data;
      int i;
      subscript_proxy(T *a,int b):data(a),i(b){}
      T & operator [] (int j) {return data[i+j];}
   subscript_proxy operator [] (int i)
      return subscript_proxy(data,i*cols);
or build an array of T*s in the ctor

template<class T,size_t rows,size_t cols>
class Matrix
   T data[rows*cols];
   T *row_start[rows];
      T *p = data;
      for(int i=0;i!=rows;++i,p+=cols)
         row_start[i] = p;
   T * operator [] (int i) {return row_start[i];}

now Matrix A;
      x = A[i][j] first calls Matrix::operator [](i) and then the
operator [](j) [either the built in for double * , or
subscript_proxy::operator [] depending on which of above
implementations is used ]

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