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C++ Programming Code Examples

C++ > Code Snippets Code Examples

Don't need a cast to go up the inheritance hierarchy

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/* Don't need a cast to go up the inheritance hierarchy */ class Base{ public: Base() {}; virtual ~Base() {} }; class Derived : public Base{ public: Derived() {} virtual ~Derived() {} }; int main(int argc, char** argv) { Base* b; Derived* d = new Derived(); b = d; // Don.t need a cast to go up the inheritance hierarchy d = static_cast<Derived*>(b); // Need a cast to go down the hierarchy Base base; Derived derived; Base& br = base; Derived& dr = static_cast<Derived&>(br); int i = 3; double result = static_cast<double>(i) / 10; return (0); }
Static Casting in C++
Static Cast: This is the simplest type of cast which can be used. It is a compile time cast.It does things like implicit conversions between types (such as int to float, or pointer to void*), and it can also call explicit conversion functions (or implicit ones). The static_cast is used for the normal/ordinary type conversion. This is also the cast responsible for implicit type coercion and can also be called explicitly. You should use it in cases like converting float to int, char to int, etc. This can cast related type classes. If you want to perform any type of conversion that is based on compile-time (static) inference, this is the way to go. We can do the common C-type casting using static_cast(), such as converting an int to a float, and vice-versa. Similarly, we can also convert between pointers and references.
new_type value = static_cast <new_type> (expression);
This will return a value of type new_type, after casting expression.
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/* A Cast operator is an unary operator which forces one data type to be converted into another data type. */ /* static_cast converts between types using a combination of implicit and user-defined conversions. */ #include <iostream> #include <string> using namespace std; class Int { int x; public: Int(int x_in = 0) : x{ x_in } { cout << "Conversion Ctor called" << endl; } operator string() { cout << "Conversion Operator" << endl; return to_string(x); } }; int main() { Int obj(3); string str = obj; obj = 20; string str2 = static_cast<string>(obj); obj = static_cast<Int>(30); return 0; }
Memory Management new Operator in C++
Allocate storage space. Default allocation functions (single-object form). A new operator is used to create the object while a delete operator is used to delete the object. When the object is created by using the new operator, then the object will exist until we explicitly use the delete operator to delete the object. Therefore, we can say that the lifetime of the object is not related to the block structure of the program.
Syntax for new Operator in C++
#include <new> //throwing (1) void* operator new (std::size_t size); //nothrow (2) void* operator new (std::size_t size, const std::nothrow_t& nothrow_value) noexcept; //placement (3) void* operator new (std::size_t size, void* ptr) noexcept;
size
Size in bytes of the requested memory block. This is the size of the type specifier in the new-expression when called automatically by such an expression. If this argument is zero, the function still returns a distinct non-null pointer on success (although dereferencing this pointer leads to undefined behavior). size_t is an integral type.
nothrow_value
The constant nothrow. This parameter is only used to distinguish it from the first version with an overloaded version. When the nothrow constant is passed as second parameter to operator new, operator new returns a null-pointer on failure instead of throwing a bad_alloc exception. nothrow_t is the type of constant nothrow.
ptr
A pointer to an already-allocated memory block of the proper size. If called by a new-expression, the object is initialized (or constructed) at this location. For the first and second versions, function returns a pointer to the newly allocated storage space. For the third version, ptr is returned. • (1) throwing allocation: Allocates size bytes of storage, suitably aligned to represent any object of that size, and returns a non-null pointer to the first byte of this block. On failure, it throws a bad_alloc exception. • (2) nothrow allocation: Same as above (1), except that on failure it returns a null pointer instead of throwing an exception. The default definition allocates memory by calling the the first version: ::operator new (size). If replaced, both the first and second versions shall return pointers with identical properties. • (3) placement: Simply returns ptr (no storage is allocated). Notice though that, if the function is called by a new-expression, the proper initialization will be performed (for class objects, this includes calling its default constructor). The default allocation and deallocation functions are special components of the standard library; They have the following unique properties: • Global: All three versions of operator new are declared in the global namespace, not within the std namespace. • Implicit: The allocating versions ((1) and (2)) are implicitly declared in every translation unit of a C++ program, no matter whether header <new> is included or not. • Replaceable: The allocating versions ((1) and (2)) are also replaceable: A program may provide its own definition that replaces the one provided by default to produce the result described above, or can overload it for specific types. If set_new_handler has been used to define a new_handler function, this new-handler function is called by the default definitions of the allocating versions ((1) and (2)) if they fail to allocate the requested storage. operator new can be called explicitly as a regular function, but in C++, new is an operator with a very specific behavior: An expression with the new operator, first calls function operator new (i.e., this function) with the size of its type specifier as first argument, and if this is successful, it then automatically initializes or constructs the object (if needed). Finally, the expression evaluates as a pointer to the appropriate type.
Data races
Modifies the storage referenced by the returned value. Calls to allocation and deallocation functions that reuse the same unit of storage shall occur in a single total order where each deallocation happens entirely before the next allocation. This shall also apply to the observable behavior of custom replacements for this function.
Exception safety
The first version (1) throws bad_alloc if it fails to allocate storage. Otherwise, it throws no exceptions (no-throw guarantee).
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/* C++ allows us to allocate the memory of a variable or an array in run time. This is known as dynamic memory allocation. The new operator denotes a request for memory allocation on the Free Store. If sufficient memory is available, new operator initializes the memory and returns the address of the newly allocated and initialized memory to the pointer variable. */ /* Allocate storage space by operator new */ // C++ program code example to illustrate dynamic allocation and deallocation of memory using new and delete #include <iostream> using namespace std; int main () { // Pointer initialization to null int* p = NULL; // Request memory for the variable // using new operator p = new(nothrow) int; if (!p) cout << "allocation of memory failed\n"; else { // Store value at allocated address *p = 29; cout << "Value of p: " << *p << endl; } // Request block of memory // using new operator float *r = new float(75.25); cout << "Value of r: " << *r << endl; // Request block of memory of size n int n = 5; int *q = new(nothrow) int[n]; if (!q) cout << "allocation of memory failed\n"; else { for (int i = 0; i < n; i++) q[i] = i+1; cout << "Value store in block of memory: "; for (int i = 0; i < n; i++) cout << q[i] << " "; } // freed the allocated memory delete p; delete r; // freed the block of allocated memory delete[] q; return 0; }
Iterators in C++ Language
Iterators are just like pointers used to access the container elements. Iterators are one of the four pillars of the Standard Template Library or STL in C++. An iterator is used to point to the memory address of the STL container classes. For better understanding, you can relate them with a pointer, to some extent. Iterators act as a bridge that connects algorithms to STL containers and allows the modifications of the data present inside the container. They allow you to iterate over the container, access and assign the values, and run different operators over them, to get the desired result.
Syntax for Iterators in C++
<ContainerType> :: iterator; <ContainerType> :: const_iterator;
• Iterators are used to traverse from one element to another element, a process is known as iterating through the container. • The main advantage of an iterator is to provide a common interface for all the containers type. • Iterators make the algorithm independent of the type of the container used. • Iterators provide a generic approach to navigate through the elements of a container. Operator (*) : The '*' operator returns the element of the current position pointed by the iterator. Operator (++) : The '++' operator increments the iterator by one. Therefore, an iterator points to the next element of the container. Operator (==) and Operator (!=) : Both these operators determine whether the two iterators point to the same position or not. Operator (=) : The '=' operator assigns the iterator. Iterators can be smart pointers which allow to iterate over the complex data structures. A Container provides its iterator type. Therefore, we can say that the iterators have the common interface with different container type. The container classes provide two basic member functions that allow to iterate or move through the elements of a container: begin(): The begin() function returns an iterator pointing to the first element of the container. end(): The end() function returns an iterator pointing to the past-the-last element of the container. Input Iterator: An input iterator is an iterator used to access the elements from the container, but it does not modify the value of a container. Operators used for an input iterator are: Increment operator(++), Equal operator(==), Not equal operator(!=), Dereference operator(*). Output Iterator: An output iterator is an iterator used to modify the value of a container, but it does not read the value from a container. Therefore, we can say that an output iterator is a write-only iterator. Operators used for an output iterator are: Increment operator(++), Assignment operator(=). Forward Iterator: A forward iterator is an iterator used to read and write to a container. It is a multi-pass iterator. Operators used for a Forward iterator are: Increment operator(++), Assignment operator(=), Equal operator(=), Not equal operator(!=). Bidirectional iterator: A bidirectional iterator is an iterator supports all the features of a forward iterator plus it adds one more feature, i.e., decrement operator(--). We can move backward by decrementing an iterator. Operators used for a Bidirectional iterator are: Increment operator(++), Assignment operator(=), Equal operator(=), Not equal operator(!=), Decrement operator(--). Random Access Iterator: A Random Access iterator is an iterator provides random access of an element at an arbitrary location. It has all the features of a bidirectional iterator plus it adds one more feature, i.e., pointer addition and pointer subtraction to provide random access to an element. Following are the disadvantages of an iterator: • If we want to move from one data structure to another at the same time, iterators won't work. • If we want to update the structure which is being iterated, an iterator won?t allow us to do because of the way it stores the position. • If we want to backtrack while processing through a list, the iterator will not work in this case. Following are the advantages of an iterator: • Ease in programming: It is convenient to use iterators rather than using a subscript operator[] to access the elements of a container. If we use subscript operator[] to access the elements, then we need to keep the track of the number of elements added at the runtime, but this would not happen in the case of an iterator. • Code Reusability: A code can be reused if we use iterators. In the above example, if we replace vector with the list, and then the subscript operator[] would not work to access the elements as the list does not support the random access. However, we use iterators to access the elements, then we can also access the list elements. • Dynamic Processing: C++ iterators provide the facility to add or delete the data dynamically.
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/* Iterators in C++ language */ // C++ code to demonstrate the working of next() and prev() #include<iostream> #include<iterator> // for iterators #include<vector> // for vectors using namespace std; int main() { vector<int> ar = { 1, 2, 3, 4, 5 }; // Declaring iterators to a vector vector<int>::iterator ptr = ar.begin(); vector<int>::iterator ftr = ar.end(); // Using next() to return new iterator // points to 4 auto it = next(ptr, 3); // Using prev() to return new iterator // points to 3 auto it1 = prev(ftr, 3); // Displaying iterator position cout << "The position of new iterator using next() is : "; cout << *it << " "; cout << endl; // Displaying iterator position cout << "The position of new iterator using prev() is : "; cout << *it1 << " "; cout << endl; return 0; }
Classes and Objects in C++ Language
The main purpose of C++ programming is to add object orientation to the C programming language and classes are the central feature of C++ that supports object-oriented programming and are often called user-defined types. A class is used to specify the form of an object and it combines data representation and methods for manipulating that data into one neat package. The data and functions within a class are called members of the class.
C++ Class Definitions
When you define a class, you define a blueprint for a data type. This doesn't actually define any data, but it does define what the class name means, that is, what an object of the class will consist of and what operations can be performed on such an object. A class definition starts with the keyword class followed by the class name; and the class body, enclosed by a pair of curly braces. A class definition must be followed either by a semicolon or a list of declarations. For example, we defined the Box data type using the keyword class as follows:
class Box { public: double length; // Length of a box double breadth; // Breadth of a box double height; // Height of a box };
The keyword public determines the access attributes of the members of the class that follows it. A public member can be accessed from outside the class anywhere within the scope of the class object. You can also specify the members of a class as private or protected which we will discuss in a sub-section.
Define C++ Objects
A class provides the blueprints for objects, so basically an object is created from a class. We declare objects of a class with exactly the same sort of declaration that we declare variables of basic types. Following statements declare two objects of class Box:
Box Box1; // Declare Box1 of type Box Box Box2; // Declare Box2 of type Box
Both of the objects Box1 and Box2 will have their own copy of data members.
Accessing the Data Members
The public data members of objects of a class can be accessed using the direct member access operator (.). It is important to note that private and protected members can not be accessed directly using direct member access operator (.).
Classes and Objects in Detail
There are further interesting concepts related to C++ Classes and Objects which we will discuss in various sub-sections listed below: • Class Member Functions: A member function of a class is a function that has its definition or its prototype within the class definition like any other variable. • Class Access Modifiers: A class member can be defined as public, private or protected. By default members would be assumed as private. • Constructor & Destructor: A class constructor is a special function in a class that is called when a new object of the class is created. A destructor is also a special function which is called when created object is deleted. • Copy Constructor: The copy constructor is a constructor which creates an object by initializing it with an object of the same class, which has been created previously. • Friend Functions: A friend function is permitted full access to private and protected members of a class. • Inline Functions: With an inline function, the compiler tries to expand the code in the body of the function in place of a call to the function. • this Pointer: Every object has a special pointer this which points to the object itself. • Pointer to C++ Classes: A pointer to a class is done exactly the same way a pointer to a structure is. In fact a class is really just a structure with functions in it. • Static Members of a Class: Both data members and function members of a class can be declared as static.
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/* using public and private in C++ Class */ // Program to illustrate the working of // public and private in C++ Class #include <iostream> using namespace std; class Room { private: double length; double breadth; double height; public: // function to initialize private variables void initData(double len, double brth, double hgt) { length = len; breadth = brth; height = hgt; } double calculateArea() { return length * breadth; } double calculateVolume() { return length * breadth * height; } }; int main() { // create object of Room class Room room1; // pass the values of private variables as arguments room1.initData(42.5, 30.8, 19.2); cout << "Area of Room = " << room1.calculateArea() << endl; cout << "Volume of Room = " << room1.calculateVolume() << endl; return 0; }
main() Function in C++
A program shall contain a global function named main, which is the designated start of the program in hosted environment. main() function is the entry point of any C++ program. It is the point at which execution of program is started. When a C++ program is executed, the execution control goes directly to the main() function. Every C++ program have a main() function.
Syntax for main() Function in C++
void main() { ............ ............ }
void
void is a keyword in C++ language, void means nothing, whenever we use void as a function return type then that function nothing return. here main() function no return any value.
main
main is a name of function which is predefined function in C++ library. In place of void we can also use int return type of main() function, at that time main() return integer type value. 1) It cannot be used anywhere in the program a) in particular, it cannot be called recursively b) its address cannot be taken 2) It cannot be predefined and cannot be overloaded: effectively, the name main in the global namespace is reserved for functions (although it can be used to name classes, namespaces, enumerations, and any entity in a non-global namespace, except that a function called "main" cannot be declared with C language linkage in any namespace). 3) It cannot be defined as deleted or (since C++11) declared with C language linkage, constexpr (since C++11), consteval (since C++20), inline, or static. 4) The body of the main function does not need to contain the return statement: if control reaches the end of main without encountering a return statement, the effect is that of executing return 0;. 5) Execution of the return (or the implicit return upon reaching the end of main) is equivalent to first leaving the function normally (which destroys the objects with automatic storage duration) and then calling std::exit with the same argument as the argument of the return. (std::exit then destroys static objects and terminates the program). 6) (since C++14) The return type of the main function cannot be deduced (auto main() {... is not allowed). 7) (since C++20) The main function cannot be a coroutine.
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/* simple code example by main() function in C++ */ #include <iostream> using namespace std; int main() { int day = 4; switch (day) { case 1: cout << "Monday"; break; case 2: cout << "Tuesday"; break; case 3: cout << "Wednesday"; break; case 4: cout << "Thursday"; break; case 5: cout << "Friday"; break; case 6: cout << "Saturday"; break; case 7: cout << "Sunday"; break; } return 0; }
Inheritance in C++
In C++, inheritance is a process in which one object acquires all the properties and behaviors of its parent object automatically. In such way, you can reuse, extend or modify the attributes and behaviors which are defined in other class. In C++, the class which inherits the members of another class is called derived class and the class whose members are inherited is called base class. The derived class is the specialized class for the base class.
Advantage of C++ Inheritance
You can reuse the members of your parent class. So, there is no need to define the member again. So less code is required in the class. Base and Derived Classes: A class can be derived from more than one classes, which means it can inherit data and functions from multiple base classes. To define a derived class, we use a class derivation list to specify the base class(es). A class derivation list names one or more base classes and has the form:
class derived-class: access-specifier base-class
Where access-specifier is one of public, protected, or private, and base-class is the name of a previously defined class. If the access-specifier is not used, then it is private by default.
C++ Single Inheritance
Single inheritance is defined as the inheritance in which a derived class is inherited from the only one base class. How to make a Private Member Inheritable: The private member is not inheritable. If we modify the visibility mode by making it public, but this takes away the advantage of data hiding. C++ introduces a third visibility modifier, i.e., protected. The member which is declared as protected will be accessible to all the member functions within the class as well as the class immediately derived from it. Visibility modes can be classified into three categories: • Public: When the member is declared as public, it is accessible to all the functions of the program. • Private: When the member is declared as private, it is accessible within the class only. • Protected: When the member is declared as protected, it is accessible within its own class as well as the class immediately derived from it.
C++ Multilevel Inheritance
Multilevel inheritance is a process of deriving a class from another derived class. When one class inherits another class which is further inherited by another class, it is known as multi level inheritance in C++. Inheritance is transitive so the last derived class acquires all the members of all its base classes.
C++ Multiple Inheritance
Multiple inheritance is the process of deriving a new class that inherits the attributes from two or more classes.
Ambiquity Resolution in Inheritance
Ambiguity can be occurred in using the multiple inheritance when a function with the same name occurs in more than one base class.
C++ Hybrid Inheritance
Hybrid inheritance is a combination of more than one type of inheritance.
C++ Hierarchical Inheritance
Hierarchical inheritance is defined as the process of deriving more than one class from a base class.
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/* Inheritance is one of the key features of Object-oriented programming in C++. It allows us to create a new class (derived class) from an existing class (base class). */ #include <iostream> using namespace std; // Base class Shape class Shape { public: void setWidth(int w) { width = w; } void setHeight(int h) { height = h; } protected: int width; int height; }; // Base class PaintCost class PaintCost { public: int getCost(int area) { return area * 70; } }; // Derived class class Rectangle: public Shape, public PaintCost { public: int getArea() { return (width * height); } }; int main(void) { Rectangle Rect; int area; Rect.setWidth(5); Rect.setHeight(7); area = Rect.getArea(); // Print the area of the object. cout << "Total area: " << Rect.getArea() << endl; // Print the total cost of painting cout << "Total paint cost: $" << Rect.getCost(area) << endl; return 0; }
Virtual Functions in C++
A C++ virtual function is a member function in the base class that you redefine in a derived class. It is declared using the virtual keyword. It is used to tell the compiler to perform dynamic linkage or late binding on the function. There is a necessity to use the single pointer to refer to all the objects of the different classes. So, we create the pointer to the base class that refers to all the derived objects. But, when base class pointer contains the address of the derived class object, always executes the base class function. This issue can only be resolved by using the 'virtual' function. A 'virtual' is a keyword preceding the normal declaration of a function. When the function is made virtual, C++ determines which function is to be invoked at the runtime based on the type of the object pointed by the base class pointer. In late binding function call is resolved during runtime. Therefore compiler determines the type of object at runtime, and then binds the function call. • Virtual functions must be members of some class. • Virtual functions cannot be static members. • They are accessed through object pointers. • They can be a friend of another class. • A virtual function must be defined in the base class, even though it is not used. • The prototypes of a virtual function of the base class and all the derived classes must be identical. If the two functions with the same name but different prototypes, C++ will consider them as the overloaded functions. • We cannot have a virtual constructor, but we can have a virtual destructor. • Consider the situation when we don't use the virtual keyword. A virtual function is not used for performing any task. It only serves as a placeholder. When the function has no definition, such function is known as "do-nothing" function. The "do-nothing" function is known as a pure virtual function. A pure virtual function is a function declared in the base class that has no definition relative to the base class. A class containing the pure virtual function cannot be used to declare the objects of its own, such classes are known as abstract base classes. The main objective of the base class is to provide the traits to the derived classes and to create the base pointer used for achieving the runtime polymorphism.
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// C++ program to demonstrate the use of virtual function // CPP program to illustrate concept of Virtual Functions #include<iostream> using namespace std; class base { public: virtual void print() { cout << "print base class\n"; } void show() { cout << "show base class\n"; } }; class derived : public base { public: void print() { cout << "print derived class\n"; } void show() { cout << "show derived class\n"; } }; int main() { base *bptr; derived d; bptr = &d; // Virtual function, binded at runtime bptr->print(); // Non-virtual function, binded at compile time bptr->show(); return 0; }
Constructors in C++ Language
In C++, constructor is a special method which is invoked automatically at the time of object creation. It is used to initialize the data members of new object generally. The constructor in C++ has the same name as class or structure. Constructors are special class functions which performs initialization of every object. The Compiler calls the Constructor whenever an object is created. Constructors initialize values to object members after storage is allocated to the object. Whereas, Destructor on the other hand is used to destroy the class object. • Default Constructor: A constructor which has no argument is known as default constructor. It is invoked at the time of creating object.
Syntax for Default Constructor in C++
class_name(parameter1, parameter2, ...) { // constructor Definition }
• Parameterized Constructor: In C++, a constructor with parameters is known as a parameterized constructor. This is the preferred method to initialize member data. These are the constructors with parameter. Using this Constructor you can provide different values to data members of different objects, by passing the appropriate values as argument.
Syntax for Parameterized Constructor in C++
class class_name { public: class_name(variables) //Parameterized constructor declared. { } };
• Copy Constructors: These are special type of Constructors which takes an object as argument, and is used to copy values of data members of one object into other object.
Syntax for Copy Constructors in C++
classname (const classname &obj) { // body of constructor }
The copy constructor is a constructor which creates an object by initializing it with an object of the same class, which has been created previously. The copy constructor is used to - • Initialize one object from another of the same type. • Copy an object to pass it as an argument to a function. • Copy an object to return it from a function. If a copy constructor is not defined in a class, the compiler itself defines one.If the class has pointer variables and has some dynamic memory allocations, then it is a must to have a copy constructor. The most common form of copy constructor is shown here.
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/* A constructor is a special type of member function that is called automatically when an object is created. In C++, a constructor has the same name as that of the class and it does not have a return type. */ #include <iostream> using namespace std; // declare a class class Wall { private: double length; double height; public: // initialize variables with parameterized constructor Wall(double len, double hgt) { length = len; height = hgt; } // copy constructor with a Wall object as parameter // copies data of the obj parameter Wall(Wall &obj) { length = obj.length; height = obj.height; } double calculateArea() { return length * height; } }; int main() { // create an object of Wall class Wall wall1(10.5, 8.6); // copy contents of wall1 to wall2 Wall wall2 = wall1; // print areas of wall1 and wall2 cout << "Area of Wall 1: " << wall1.calculateArea() << endl; cout << "Area of Wall 2: " << wall2.calculateArea(); return 0; }
Reverse Iterator base() Function in C++
Return base iterator. Returns a copy of the base iterator. The base iterator is an iterator of the same type as the one used to construct the reverse_iterator, but pointing to the element next to the one the reverse_iterator is currently pointing to (a reverse_iterator has always an offset of -1 with respect to its base iterator).
Syntax for reverse_iterator base() Function in C++
#include <iterator> iterator_type base() const;
The function does not accept any parameter. Function returns a copy of the base iterator, which iterates in the opposite direction. Member type iterator_type is the underlying bidirectional iterator type (the class template parameter: Iterator).
Data races
The object is accessed. The iterator returned can be used to access or modify elements.
Exception safety
Provides the same level of guarantee as the copy constructor of the base iterator.
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/* Returns the underlying base iterator. That is std::reverse_iterator(it).base() == it. The base iterator refers to the element that is next (from the std::reverse_iterator::iterator_type perspective) to the element the reverse_iterator is currently pointing to. That is &*(rit.base() - 1) == &*rit. */ /* Return base iterator by reverse_iterator::base code example */ #include <iostream> // std::cout #include <iterator> // std::reverse_iterator #include <vector> // std::vector int main () { std::vector<int> myvector; for (int i=0; i<10; i++) myvector.push_back(i); typedef std::vector<int>::iterator iter_type; std::reverse_iterator<iter_type> rev_end (myvector.begin()); std::reverse_iterator<iter_type> rev_begin (myvector.end()); std::cout << "myvector:"; for (iter_type it = rev_end.base(); it != rev_begin.base(); ++it) std::cout << ' ' << *it; std::cout << '\n'; return 0; }
Destructors in C++
A destructor is a special member function that works just opposite to constructor, unlike constructors that are used for initializing an object, destructors destroy (or delete) the object. Destructors in C++ are members functions in a class that delete an object. They are called when the class object goes out of scope such as when the function ends, the program ends, a delete variable is called etc. Destructors are different from normal member functions as they don't take any argument and don't return anything. Also, destructors have the same name as their class and their name is preceded by a tilde(~).
Syntax for Destructor in C++
~class_name() { //Some code }
Similar to constructor, the destructor name should exactly match with the class name. A destructor declaration should always begin with the tilde(~) symbol as shown in the syntax above. A destructor is automatically called when: • The program finished execution. • When a scope (the { } parenthesis) containing local variable ends. • When you call the delete operator.
Destructor rules
• Name should begin with tilde sign(~) and must match class name. • There cannot be more than one destructor in a class. • Unlike constructors that can have parameters, destructors do not allow any parameter. • They do not have any return type, just like constructors. • When you do not specify any destructor in a class, compiler generates a default destructor and inserts it into your code.
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/* Destructor is an instance member function which is invoked automatically whenever an object is going to be destroyed. Meaning, a destructor is the last function that is going to be called before an object is destroyed. The thing is to be noted here, if the object is created by using new or the constructor uses new to allocate memory which resides in the heap memory or the free store, the destructor should use delete to free the memory. */ #include <iostream> using namespace std; class HelloWorld{ public: //Constructor HelloWorld(){ cout<<"Constructor is called"<<endl; } //Destructor ~HelloWorld(){ cout<<"Destructor is called"<<endl; } //Member function void display(){ cout<<"Hello World!"<<endl; } }; int main(){ //Object created HelloWorld obj; //Member function called obj.display(); return 0; }
Casting Operators in C++
A cast is a special operator that forces one data type to be converted into another. As an operator, a cast is unary and has the same precedence as any other unary operator. Converting an expression of a given type into another type is known as type-casting. The most general cast supported by most of the C++ compilers is as follows:
(type) expression
Where type is the desired data type. There are other casting operators supported by C++, they are listed below: • const_cast<type> (expr): The const_cast operator is used to explicitly override const and/or volatile in a cast. The target type must be the same as the source type except for the alteration of its const or volatile attributes. This type of casting manipulates the const attribute of the passed object, either to be set or removed. • dynamic_cast<type> (expr): The dynamic_cast performs a runtime cast that verifies the validity of the cast. If the cast cannot be made, the cast fails and the expression evaluates to null. A dynamic_cast performs casts on polymorphic types and can cast a A* pointer into a B* pointer only if the object being pointed to actually is a B object. • reinterpret_cast<type> (expr): The reinterpret_cast operator changes a pointer to any other type of pointer. It also allows casting from pointer to an integer type and vice versa. • static_cast<type> (expr): The static_cast operator performs a nonpolymorphic cast. For example, it can be used to cast a base class pointer into a derived class pointer. All of the above-mentioned casting operators will be used while working with classes and objects. For now, try the following example to understand a simple cast operators available in C++. Copy and paste the following C++ program in test.cpp file and compile and run this program.
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/* Type casting of the variables in the C++ programming language. Type casting refers to the conversion of one data type to another in a program. Typecasting can be done in two ways: automatically by the compiler and manually by the programmer or user. Type Casting is also known as Type Conversion. */ /* code example to demonstrate the casting of one variable to another using the implicit type casting in C++. */ #include <iostream> using namespace std; int main () { short x = 200; int y; y = x; cout << " Implicit Type Casting " << endl; cout << " The value of x: " << x << endl; cout << " The value of y: " << y << endl; int num = 20; char ch = 'a'; int res = 20 + 'a'; cout << " Type casting char to int data type ('a' to 20): " << res << endl; float val = num + 'A'; cout << " Type casting from int data to float type: " << val << endl; return 0; }


2 const variables row & col are used to define size. If we do not make both const then error found because without "const reserve word" they are behaving as variable. Before placing
C++ program, without recursion, displays the nodes of a "Particular Binary Tree" in inorder fashion without using recursive traversal. So Enter value of root node. Enter value of node
First ask to enter the array size then it will ask to enter the array elements, then it will finally ask to enter a number to be search in array to check whether it is present in the array or not