Assignment Operators in C++ are the symbols utilized to allocate values to variables. They execute straightforward value allocations and can also integrate with both arithmetic and bitwise operators. In this article, we will explore what an assignment operator in C++ is, its various types along with examples in C++, the chaining of assignment operators, limitations, and recommended practices.
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Output:
The code illustrates how the simple assignment operator is employed to allocate the value 10 to the variable a and the value 20 to the variable b, subsequently displaying the assigned variables as output in the console.
2. Compound Assignment Operators
Compound assignment operators are a blend of elementary arithmetic
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and bitwise operators alongside the assignment operator.
Syntax:
variable op= expression;
Below is the enumeration of all compound assignment operators in C++:
Operator Name
Symbol
Syntax
Description
Add and assign
+=
a += b;
Adds b to a and saves the outcome in a
Subtract and assign
-=
a -= b;
Deducts b from a and saves the result
Multiply and assign
*=
a *= b;
Multiplies a with b and updates a
Divide and assign
/=
a /= b;
Divides a by b and modifies a
Modulo and assign
%=
a %= b;
Calculates a % b and saves the outcome in a
Bitwise AND and assign
&=
a &= b;
Executes bitwise AND on a and b, updates a
Bitwise OR and assign
|=
a |= b;
Executes bitwise OR on a and b, updates a
Bitwise XOR and assign
^=
a ^= b;
Executes bitwise XOR on a and b, updates a
Left shift and assign
<<=
a <<= b;
Shifts a to the left by b bits and updates a
Right shift and assign
>>=
a >>= b;
Shifts a to the right by b bits and updates a
Example:
Cpp
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Output:
This code illustrates how different compound assignment operators function to execute fundamental mathematical operations and subsequently update a value within the same variable.
Chaining the Assignment Operator in C++
Chaining the assignment operator in C++ refers to the process of assigning an identical value to multiple variables within a single statement utilizing the assignment operator (=). This is possible because the assignment operator provides a reference to the variable on the left side, facilitating additional assignments.
Syntax:
a = b = c = value;
Example:
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Outcome:
The program illustrates how the value 100 is initially assigned to the variable c, subsequently to the variable b, and finally to the variable a through chained assignment, resulting in all three variables possessing the identical value.
Assignment Across Different Classes in C++
Assignment between distinct classes in C++ can only occur if the following conditions are satisfied:
A suitable conversion function must exist.
An appropriate assignment operator needs to be overloaded.
Scenario 1: Utilizing Conversion Constructor
In this method, class B features a constructor that accepts an object of class A, and when an object of type A is assigned to an object of type B, the compiler automatically invokes this constructor to convert A into B.
Illustration:
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Result:
This code illustrates that class B includes a conversion constructor, which facilitates the initialization of class B using an instance of class A by allowing the statement B b = a;, and subsequently, the assigned result is displayed as output.
Case 2: Operator Overloading for Assignment
In this method, class B overloads the assignment operator to accept an instance of class A. This enables an already existing instance of class B to receive values from an instance of class A utilizing the syntax b = a;, along with the custom logic specified in the operator function.
Illustration:
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Result:
The code demonstrates how class B overloads the assignment operator to accept an instance of class A, facilitating the assignment b = a; to transfer the data from class A to class B.
Drawbacks of the Assignment Operator in C++
In C++, assignment operators are not inherited by derived classes and must be explicitly defined.
The default assignment operator executes a shallow copy, which might cause issues related to pointers and dynamic memory.
If self-assignment is not handled correctly, it may lead to bugs or resource conflicts.
The assignment operator needs to be manually overloaded for deep copying.
An assignment between incompatible types is prohibited unless explicitly defined.
Classes with const or reference members cannot reassign those members within the assignment operator.
If certain special member functions are defined, the compiler may not create a default assignment operator.
Best Practices for Implementing the Assignment Operator in C++
Always verify for self-assignment.
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You should return *this by reference to facilitate chained assignments.
Always designate the assignment operator as =, and remove it if your class cannot be duplicated.
You ought to apply the copy-and-swap idiom to formulate safer and exception-safe assignment logic.
If you are required to implement a copy assignment, you must create a copy constructor.
Ensure the assignment operator is coherent with the copy and move semantics of the class.
Utilize const references in the parameters to prevent unnecessary duplication.
You need to guarantee exception safety to avoid resource leaks during partial assignments.
Conclusion
The assignment operator in C++ is a crucial operator for storing values in variables. It also permits chaining and assignments across different classes in C++. There are numerous assignment methods that efficiently store values, yet they also come with certain restrictions. Hence, by comprehending the assignment operator along with its variations, constraints, and recommended practices, you can write effective and maintainable C++ code.
Assignment Operators in C++ – FAQs
Q1. What is the assignment operator in C++?
The assignment operator is the mechanism that assigns the value on the right-hand side to the variable on the left-hand side using =.
Q2. What is a chained assignment?
Chained assignment refers to the action of assigning the same value to multiple variables within a single statement.
Q3. Can we assign between different classes?
Indeed, it is possible to assign between different classes using a conversion constructor along with an overloaded assignment operator.
Q4. What is the risk of default assignment?
The default assignment performs a shallow copy, which may result in complications regarding dynamic memory.
Q5. Why do I have to check for self-assignment?
It is essential to check for self-assignment to prevent bugs and resource mismanagement when an object is assigned to itself.
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