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Pointers and References and Function Objects
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- 9. What is aReference? A reference is an alias for an already existing variable. Declared using the ampersand (&) operator (e.g., int& ref;) Must be initialized when declared Cannot be nullptr Cannot be reassigned to another variable Dereferenced implicitly Arithmetic operations not supported
- 10. Reference - MoreExplanation References provide safer, simpler access to variables. Commonly used in function parameters and return types Ideal for avoiding copying of large data Often used in operator overloading int b = 20; int& ref = b;
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- 13. Conclusion Pointers: Usewhen dynamic memory allocation or pointer arithmetic is needed. References: Use when you need a simple alias for passing parameters or returning values without copying. Prefer references over pointers when null values and reassignment are not needed.
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- 15. Function Objects (Functors) These are objects of a class that overload the function call operator (operator()), allowing them to be called like functions. Definition: A class is created with a public operator() member function. Usage: Instances of this class can then be "called" with arguments, just like regular functions. Benefits: Functors can maintain state (data members) between calls, unlike plain functions. They are widely used in the C++ Standard Library, particularly with algorithms and containers for custom operations (e.g., custom sorting criteria).
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- 18. Classes & Structures In C++, both classes and structures are user-defined data types that allow grouping data members and member functions into a single unit. They serve as blueprints for creating objects, which are instances of these types.
- 19. Classes Defined usingthe class Keyword. By default, members (data and functions) within a class are private. This means they can only be accessed from within the class itself or by its friend functions/classes. Classes are fundamental to Object-Oriented Programming (OOP) in C++ and are commonly used to encapsulate data and behavior, providing controlled access through public interfaces. Support advanced OOP concepts like inheritance and polymorphism.
- 21. Structures: Defined usingthe struct keyword. By default, members within a structure are public. This means they can be accessed directly from outside the structure. Historically, structures in C were primarily used to group related data. In C++, structures have been extended to also include member functions, constructors, destructors, and support inheritance, making them almost identical to classes in functionality. Often used for simple data structures where public access to members is acceptable or when interfacing with C code that uses structures.
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- 24. FRIEND FUNCTIONS Afriend function is a function which is declared within a class and is defined outside the class. It does not require any scope resolution operator for defining. It can access private members of a class. It is declared by using keyword “friend”. The scope resolution operator :: allows us to define a member function of a class outside the class definition.
- 25. How to declareFriend Function : Friend function declaration should be inside the class using the Friend key word. Syntax: friend ret_type func_name(arguments); Definition of friend function is specified outside the class. Function definition must not use keyword friend.
- 26. Friend function characterstics: It is not in scope of class. It cannot be called using object of that class. It can be invoked like a normal function. It has objects as arguments. Friend Functions are majorly used in operator overlading. Friendship is not inherited by derived classes.
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- 29. Inline Functions: C++inline function is powerful concept that is commonly used with classes. If a function is inline, the compiler places a copy of the code of that function at each point where the function is called at compile time. Any change to an inline function could require all clients of the function to be recompiled because compiler would need to replace all the code once again otherwise it will continue with old functionality.
- 30. Defining an InlineFunction To define an inline function, place the keyword inline before the function name and define the function before any calls are made to the function. The compiler can ignore the inline qualifier in case defined function is more than a line. inline int Max(int x, int y) { return (x > y)? x : y; }
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- 33. Passing an Objectas argument To pass an object as an argument we write the object name as the argument while calling the function the same way we do it for other variables. Syntax: function_name(object_name);
- 35. Returning objects fromfunctions In C++, a function can return an object of a class. This helps send complete data (like multiple values) from the function back to the main program. The returned object can be used to call its methods or access its data. This is useful in object-oriented programming for better data handling.
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- 37. Pass by Value& Pass by Reference in C++
- 38. In C++,data can be sent to functions when they are called in order to perform operations. This data is called parameters or arguments and there are various parameter passing methods available in C++. Before you see the techniques, first understand the difference between the following terms: Formal Parameters: Variables used in parameter list of a function as placeholders. Also called only parameters. Actual Parameters: The expressions or values passed in during a function call. Also called arguments. There are 3 different methods using which we can pass parameters to a function in C++. These are: Table of Content Pass by Value Pass by Reference Pass by Pointer
- 39. Pass by Value In pass by value method, a variable's value is copied and then passed to the function. As the result, any changes to the parameter inside the function will not affect the variable's original value in the caller. This method is simple, easy to understand and implement but it is not preferred for large size of data structures at it involves copying the value.
- 40. Pass By Value #include<iostream> using namespace std; int change(int a) { a = 22; return a; } int main() { int x = 5; cout << x<<endl; cout << change(x)<<endl; cout << x; return 0; }
- 41. Pass By Reference In pass-by-reference method, instead of passing the value of the argument, we pass the reference of an argument to the function. This allows the function to change the value of the original argument. This is useful when you have to pass large size data. It is Suitable when you want to modify the original data or avoid copying large data.
- 42. Pass By Reference #include<iostream> using namespace std; int change(int &a) { a = 22; return a; } int main() { int x = 5; cout << x<<endl; cout << change(x)<<endl; cout << x; return 0; }
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