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Articles on Trending Technologies
Technical articles with clear explanations and examples
What is the copy-and-swap idiom in C++?
The assignment consists of 2 steps, tearing 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 using the swap function. The temporary copy is then destructed using the destructor. We ...
Read MoreWhy is it faster to process a sorted array than an unsorted array in C++?
In C++, it is faster to process a sorted array than an unsorted array because of branch prediction. In computer architecture, a branch prediction determines whether a conditional branch (jump) in the instruction flow of a program is likely to be taken or not.Let’s take an example −if(arr[i] > 50) { Do some operation B } else { Do some operation A }If we run this code for 100 elements in unsorted and sorted order below things will be happened −For sorted array −1, 2, 3, 4, 5, …… 50, 51………100 A, A, A, A, A A, B ...
Read MoreWhat is The Rule of Three with reference to C++?
The Rule of three is a rule of thumb when using C++. This is kind of a good practice rule that says that If your class needs any ofa copy constructor, an assignment operator, or a destructor, defined explicitly, then it is likely to need all three of them.Why is this? Its because, if your class requires any of the above, it is managing dynamically allocated resources and would likely be needing the other to successfully achieve that. For example, if you require an assignment operator, you would be creating copies of objects currently being copied by reference, hence allocating ...
Read MoreWhat are undefined reference/unresolved external symbol errors in C++?
As the name suggests, a symbol you declared was not defined by you. This may occur due to many cases. Let's have a look at three of them −You forgot to define the declared name. For example, you declared a function in a file and used it somewhere. But you did not provide its definition. Code −#include void foo(); int main() { foo(); // Declared but not defined }You defined it but did not use the qualified name. Say you created a class with a method and defined that method but forgot using scope resolution to link that function ...
Read MoreWhat are the methods supported by W3C DOM?
The following are the method supported by W3C DOM −Sr.NoProperty & Description1createAttribute( name)Returns a newly-created Attr node with the specified name.Ex − document.createAttribute( name)2createComment( text)Creates and returns a new Comment node containing the specified text.Ex − document.createComment( text)3createDocumentFragment( )Creates and returns an empty DocumentFragment node.Ex − document.createDocumentFragment( )4createElement( tagName)Creates and returns a new Element node with the specified tag name.Ex − document.createElement( tagName)5createTextNode( text)Creates and returns a new Text node that contains the specified text.Ex − document.createTextNode( text)6getElementById( id)Returns the Element of this document that has the specified value for its id attribute, or null if no such Element exists ...
Read MoreHow can I turn on error information in my Web Browser?
The most basic way to track down errors is by turning on error information in your browser. By default, Internet Explorer shows an error icon in the status bar when an error occurs on the page.Double-clicking this icon takes you to a dialog box showing information about the specific error that occurred.Since this icon is easy to overlook, Internet Explorer gives you the option to automatically show the Error dialog box whenever an error occurs.To enable this option, select Tools → Internet Options → Advanced tab. and then finally check the "Display a Notification About Every Script Error" box option ...
Read MoreWhat are Shell Commands?
The shell is the command interpreter on the Linux systems. It the program that interacts with the users in the terminal emulation window. Shell commands are instructions that instruct the system to do some action.Some of the commonly used shell commands are −basenameThis command strips the directory and suffix from filenames. It prints the name of the file with all the leading directory components removed. It also removes a trailing suffix if it is specified.Example of basename is as follows −$ basename country/city.txtThis gets the name of the file i.e. city which is present in folder country.city.txtcatThis command concatenates and ...
Read MoreWhy Java programs running on Android systems do not use the standard Java API and virtual machine?
The standard Java API and virtual machine are mainly designed for desktop as well as server systems. They are not that compatible with mobile devices. Because of this, Google has created a different API and virtual machine for mobile devices. This is known as the Dalvik virtual machine.The Dalvik virtual machine is a key component of the Android runtime and is a part of JVM (Java Virtual Machine) developed specially for Android. The Dalvik virtual machine uses features that are quite important in Java such as memory management, multi-threading etc. The programs in Java are first converted into JVM and ...
Read MoreHow we have multiple stored GENERATED COLUMNS in MySQL table with CREATE TABLE statement?
It is quite possible to add multiple stored generated columns in a MySQL table. It can be illustrated with the following example as follows −Examplemysql> Create table profit1(cost int, price int, profit int AS (price-cost) STORED, price_revised int AS (price-2) STORED); Query OK, 0 rows affected (0.36 sec) mysql> Describe profit1; +---------------+---------+------+-----+---------+------------------+ | Field | Type | Null | Key | Default | Extra | +---------------+---------+------+-----+---------+------------------+ | cost ...
Read MoreHow can we alter table to add MySQL stored GENERATED COLUMNS?
For adding MySQL stored GENERATED COLUMNS in a table, we can use the same syntax as adding a column just adding “AS(expression)” after the data type. Its syntax would be as follows −SyntaxALTER TABLE table_name ADD COLUMN column_name AS(expression)STORED;Examplemysql> ALTER TABLE employee_data_stored ADD COLUMN FULLName Varchar(200) AS (CONCAT_WS(" ", 'First_name', 'Last_name')) STORED; Query OK, 2 rows affected (1.23 sec) Records: 2 Duplicates: 0 Warnings: 0 mysql> Describe employee_data_stored; +------------+--------------+------+-----+---------+------------------+ | Field | Type | Null | Key | Default | Extra ...
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