What happens if a user forgets to define a constructor inside a class? Destructors are usually used to deallocate memory and do other cleanup for a class object and its class members when the object is destroyed. A destructor is called for a class object when that object passes out of scope or is explicitly deleted. A destructor can be declared virtual or pure virtual. Constructor helps to initialize the object of a class. Whereas destructor is used to destroy the instances. Friend functions In principle, private and protected members of a class cannot be accessed from outside the same class in which they are declared.
However, this rule does not affect friends. Explanation: All the member functions work same as normal functions with syntax. But the constructor and destructor are also considered as member functions of a class, and they never have any data type. Even though the prototypes for friend functions appear in the class definition, friends are not member functions. A friend function is declared inside the class with a friend keyword preceding as shown below. Benefits of friend function A friend function is used to access the non-public members of a class.
It allows to generate more efficient code. It provides additional functionality which is not normally used by the class. It allows to share private class information by a non member function. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Does ES6 make JavaScript frameworks obsolete?
Podcast Do polyglots have an edge when it comes to mastering programming Featured on Meta. Now live: A fully responsive profile. Linked Related Hot Network Questions. Question feed. Suggested Exams. How many different insertion sequences of the key values using the same hash function and linear probing will result in the hash table shown above?
Which one of the following choices gives a possible order in which the key values could have been inserted in the table? The following C function takes a simply-linked list as input argument. It modifies the list by moving the last element to the front of the list and returns the modified list.
Which data structure in a compiler is used for managing information about variables and their attributes? In a binary tree with n nodes, every node has an odd number of descendants. Every node is considered to be its own descendant.
What is the number of nodes in the tree that have exactly one child? We are given a set of n distinct elements and an unlabeled binary tree with n nodes. The possibility has been considered several times, but each time it was decided that the likely problems outweighed the likely benefits. Even when Stroustrup first considered it in , he knew how it could be implemented. Such problems seem prone to lead to subtle bugs. No: at least one operand of any overloaded operator must be of some user-defined type most of the time that means a class.
The names of, precedence of, associativity of, and arity of operators is fixed by the language. Besides, operator overloading is just syntactic sugar for function calls. Remember the purpose of operator overloading: to reduce the cost and defect rate in code that uses your class.
Caveat: the list is not exhaustive. Caveat: the list contains guidelines, not hard and fast rules. That means almost all of the entries have exceptions, and most of those exceptions are not explicitly stated. I know. When you have multiple subscripts, the cleanest way to do it is with operator rather than with operator[].
The reason is that operator[] always takes exactly one parameter, but operator can take any number of parameters in the case of a rectangular matrix, two parameters are needed. Then you can access an element of Matrix m using m i,j rather than m[i][j] :. See the next FAQ for more detail on the reasons to use m i,j vs. Thus they access elements of the matrix using syntax like m[i][j] rather than syntax like m i,j.
The array-of-array solution obviously works, but it is less flexible than the operator approach. Specifically, there are easy performance tuning tricks that can be done with the operator approach that are more difficult in the [][] approach, and therefore the [][] approach is more likely to lead to bad performance, at least in some cases.
In contrast, the operator approach totally hides the physical layout of the matrix, and that can lead to better performance in some cases. Put it this way: the operator approach is never worse than, and sometimes better than, the [][] approach. As an example of when a physical layout makes a significant difference, a recent project happened to access the matrix elements in columns that is, the algorithm accesses all the elements in one column, then the elements in another, etc.
Of course there are many examples of this sort of thing from numerical methods, and sparse matrices are a whole other dimension on this issue. Use the operator approach. The same reasons you encapsulate your data structures, and the same reason you check parameters to make sure they are valid.
A few people use [][] despite its limitations , arguing that [][] is better because it is faster or because it uses C-syntax.
Plus, oh yea, the C-syntax makes it harder to change the data structure and harder to check parameter values. The point of the previous two FAQs is that m i,j gives you a clean, simple way to check all the parameters and to hide and therefore, if you want to, change the internal data structure. The world already has way too many exposed data structures and way too many out-of-bounds parameters, and those cost way too much money and cause way too many delays and way too many defects.
Now everybody knows that you are different. For them, maintenance costs are high, defects are real, and requirements change. Believe it or not, every once in a while they need to better sit down change their code. Admittedly my thongue wath in my theek. But there was a point. The point was that encapsulation and parameter-checking are not crutches for the weak.
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