subscript operator overloading

[Uday]

hello friends,
i have defined a template two dimensional array. its working
fine. since the operator[] function gives me only the row index, i
couldn't catch the column index overflow. is there any way to find &
check it wothout using operator()(int row, int column) function?

Uday.

 

[Oliver Kreylos]

i have defined a template two dimensional array. its working
fine. since the operator[] function gives me only the row index, i
couldn't catch the column index overflow. is there any way to find &
check it wothout using operator()(int row, int column) function?

Interesting problem. One solution I could think of is have the
operator[] of the 2D array return not a pointer to the selected row (and
use the standard C operator[] for pointers to the column dereferencing),
but have it return a special temporary object that represents the
column, and has another overloaded operator[] to do range checking and
dereferencing. C++ compilers should be able to optimize away most -- if
not all -- the overhead inherent in creating/returning a temporary.

Hope this helps,

Oliver

 

[Uday]

thanx a lot Oliver.
now i'm able to catch the column overflow too.
thanx again.

Uday.

 

[CommeCaDuMode]

reply

If you really need Object[y][x] you may use an indirection to the object.

For instance

class Item {
  int onedim[100];
public:
  int &operator[] (int x) { return(onedim[x]); }
};

Item twodim[20];

Then to access your data

for (int j=0 ; j<20 ; j++) for (int i=0 ; i<100 ; i++) twodim[j][i] = i*j;

You may also use a vector<Item> instead of Item twodim[..]