Programming Articles - Page 2730 of 3366

The Copy and Swap Idiom in C++ is a technique used in assignment operations. This consists of two steps: Discarding an object's old state and building a new state for it. The destructor is used for the first step and a copy constructor does the second step. Implementing both of these is straightforward. But when overloading the assignment operator, it can become quite difficult to implement. The copy and swap idiom is a solution for the same. This idiom uses the copy-constructor to build a local copy of the data. It then swaps the old data with the new data ... Read More

Type inference (or, type deduction) refers to the automatic detection of the data type of an expression in a programming language. In C++, the auto keyword is used for automatic type deduction.For example, you want to create an iterator to iterate over a vector, you can simply use auto for that purpose.It is helpful, when dealing with complicated STL containers, iterators, and lambda functions where it may be hard to write the full type. This can be achieved using auto, decltype, and decltype(auto) keywords. These approaches help in letting the compiler understand the correct data types without explicitly declaring them. ... Read More

In C++, the strand sort is a recursive sorting algorithm. It is used to extract increasing subsequences repeatedly (called strands) from the input list and merge them into a sorted list. There are multiple libraries that can be used for different purposes. This sorting is one of them. This sorting technique is particularly good for sorting linked lists, but can be used with arrays too. The following is a list of approaches for strand sorting in C++: These approaches is to extract sorted strands (in increasing/descending order) from the unsorted list and merge them one by one into a final ... Read More

In this section we will see how to perform sorting algorithm in C++. A sorted array is an array in which each of the elements are sorted in some order such as numerical, alphabetical etc. There are many algorithms to sort a numerical array such as bubble sort, insertion sort, selection sort, merge sort, quick sort, heap sort etc. More details about sorting the array using selection sort are given below.The selection sort is a sorting method that yields a sorted array. It does so by repeatedly finding the smallest element in the array and interchanging it with the element ... Read More

Yes, the namespace can be nested in C++. We can define one namespace inside another namespace. This makes it easier for developers to design a more structured and hierarchical format for their code. Syntax The following is the syntax as below : namespace namespace_name1 { // code declarations namespace namespace_name2 { // code declarations } } You can access members of a nested namespace by using resolution operators as follows: // to access members of namespace_name2 ... Read More

You can add/set an auto increment constraint to a column in a table using the ALTER TABLE command.SyntaxALTER TABLE table_name ADD id INT PRIMARY KEY AUTO_INCREMENTAssume we have a table named Dispatches in the database with 7 columns namely id, CustomerName, DispatchDate, DeliveryTime, Price and, Location with description as shown below:+--------------+--------------+------+-----+---------+-------+ | Field        | Type         | Null | Key | Default | Extra | +--------------+--------------+------+-----+---------+-------+ | ProductName  | varchar(255) | YES  | UNI | NULL    | | | CustomerName | varchar(255) | YES  |     ... Read More

Consider a situation, when we have two persons with the same name, Zara, in the same class. Whenever we need to differentiate them definitely we would have to use some additional information along with their name, like either the area, if they live in different area or their mother’s or father’s name, etc.Same situation can arise in your C++ applications. For example, you might be writing some code that has a function called xyz() and there is another library available which is also having same function xyz(). Now the compiler has no way of knowing which version of xyz() function ... Read More

You can drop a constraint on a column of a table using the ALTER TABLE command.SyntaxALTER TABLE table_name DROP CONSTRAINT MyUniqueConstraint;Assume we have a table named Dispatches in the database with 7 columns namely id, CustomerName, DispatchDate, DeliveryTime, Price and, Location with description as shown below:+--------------+--------------+------+-----+---------+-------+ | Field        | Type         | Null | Key | Default | Extra | +--------------+--------------+------+-----+---------+-------+ | ProductName  | varchar(255) | YES  | UNI | NULL    | | | CustomerName | varchar(255) | YES  |     | NULL    | ... Read More

A class constructor is a special member function of a class that is executed whenever we create new objects of that class.A constructor will have exact same name as the class and it does not have any return type at all, not even void. Constructors can be very useful for setting initial values for certain member variables.Following example explains the concept of constructor −Example Live Demo#include using namespace std; class Line {    public:       void setLength( double len );       double getLength( void );       Line(); // This is the constructor       private:       double length; }; // Member functions definitions including constructor Line::Line(void) {    cout

You can add a not null constraint to a column of a table using the ALTER TABLE command.SyntaxALTER TABLE table_name MODIFY column_name datatype NOT NULL;Assume we have a table named Dispatches in the database with 7 columns namely id, CustomerName, DispatchDate, DeliveryTime, Price and, Location with description as shown below:+--------------+--------------+------+-----+---------+-------+ | Field        | Type         | Null | Key | Default | Extra | +--------------+--------------+------+-----+---------+-------+ | ProductName  | varchar(255) | YES  |     | NULL    |       | | CustomerName | varchar(255) | YES  |     | NULL   ... Read More