(Overloading the Parentheses Operator)One nice example of overloading the function call op...

(Overloading the Parentheses Operator)One nice example of overloading the function call operator () is to allow another form of double-array subscripting popular in some programming languages. Instead of saying

chessBoard[ row ][ column ]

for an array of objects, overload the function call operator to allow the alternate form

chessBoard( row, column )

Create a class DoubleSubscriptedArray that has similar features to class Array in Figs. 1– 2 At construction time, the class should be able to create an array of any number of rows and any number of columns. The class should supply operator() to perform double-subscripting operations. For example, in a 3-by-5 DoubleSubscriptedArray called a, the user could write a(1, 3) to access the element at row 1 and column 3. Remember that operator() can receive any number of arguments. The underlying representation of the double-subscripted array should be a single-subscripted array of integers with rows * columns number of elements. Function operator() shouldperform the proper pointer arithmetic to access each element of the array. There should be two versions of operator()—one that returns int&(so that an element of a DoubleSubscriptedArray can be used as an lvalue) and one that returns const int&. The class should also provide the following operators: ==, !=, =, << (for outputting the array in row and column format) and >> (for inputting the entire array contents).

Figure 1 Array class definition with overloaded operators.

Figure 2 Array class member- and friend-function definitions.