Operator overloading function can be made friend function if it needs access to the private and protected members of class. Let's see a simple example of overloading the binary operators. Program to overload the binary operators Almost all arithmetic operator can be overloaded to perform arithmetic operation on user-defined data type.
Most can be overloaded. First with out operator overloading:. There is no fundamental reason to disallow overloading of? Note that a function overloading expr1? Thus, sizeof X could not be given a new and different meaning by the programmer without violating basic language rules.
What about ::? In N::m neither N nor m are expressions with values; N and m are names known to the compiler and :: performs a compile time scope resolution rather than an expression evaluation. One could imagine allowing overloading of x::y where x is an object rather than a namespace or a class, but that would — contrary to first appearances — involve introducing new syntax to allow expr::expr. It is not obvious what benefits such a complication would bring. However, doing so can lead to questions about whether an operation is meant for the object overloading.
For example:. This problem can be solved in several ways. So far in standardization, it has not been obvious which way would be best. Sorry, no. 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. I discuss these before the arithmetic operators for a very specific reason, but we will get to that in a moment. The important point is that these are destructive operators, because they update or replace the values on the left-hand side of the assignment.
So, you write: MyClass a, b; How those values are modified isn't very important - obviously, what MyClass represents will dictate what these operators mean. And, the implementation of such an operation should also be straightforward. But, you will notice that the operator returns a MyClass -reference, and a non-const one at that.
This is so you can do things like this: MyClass mc; Don't ask me why somebody would want to do this, but just like the normal assignment operator, this is allowed by the primitive data types. Our user-defined datatypes should match the same general characteristics of the primitive data types when it comes to operators, to make sure that everything works as expected.
This is very straightforward to do. As one last note, in general you should beware of self-assignment with compound assignment operators as well.
The binary arithmetic operators are interesting because they don't modify either operand - they actually return a new value from the two arguments. Why overriding both the global new operator and the class-specific operator is not ambiguous? Article Contributed By :. Easy Normal Medium Hard Expert.
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