sk@macbeth.cs.duke.edu (Srinivasan Krishnan) (07/25/90)
While trying to implement an array based object, I have run into
difficulties with detection of writes on the array.
Here's part of the definition of the class:
class IntArray {
public :
// allows assignments of the form A = B
IntArray& operator=(const IntArray&);
// returns the lvalue of the i-th element of the array
int& operator[] (int);
protected :
// internal data representation
int flag;
int *ia;
};
I would like to be able to set the variable "flag" to zero whenever any
assignments are made to the array.
Assignments to an array are of 2 types :
1 A = B ; ( A and B IntArrays )
By overloading the = operator , I am able to
set the flag of A to 0
2 A[i] = somevalue;
This is causing the problem. The [] operator is used for
both reads and writes, and the = operator operates on integers.
Is there any way I can cause the side effect of setting flag to 0
only on memory writes while retaining the use of the [] operator?
thomasw@hpcupt1.HP.COM (Thomas Wang) (07/26/90)
Your problem is that the [] operator is defined as returning a reference. Change it to return a normal object, then add a void put_at(int, array_element_type&); -Thomas Wang (Everything is an object.) wang@hpdmsjlm.cup.hp.com thomasw@hpcupt1.cup.hp.com
roger@procase.UUCP (Roger H. Scott) (08/02/90)
I posted a detailed example of "virtual arrays" about two weeks ago. Go back and look at the last few weeks' news.