Tutorial by Examples: t

WebSocket provides a duplex/bidirectional communication protocol over a single TCP connection. the client opens a connection to a server that is listening for a WebSocket request a client connects to a server using a URI. A server may listen to requests from multiple clients. Server Endpoint...

It's best for readability (and your sanity) to avoid escaping the escapes. That's where raw strings literals come in. (Note that some languages allow delimiters, which are preferred over strings usually. But that's another section.) They usually work the same way as this answer describes: [A] ba...

In most programming languages, in order to have a backslash in a string generated from a string literal, each backslash must be doubled in the string literal. Otherwise, it will be interpreted as an escape for the next character. Unfortunately, any backslash required by the regex must be a literal ...

Character escaping is what allows certain characters (reserved by the regex engine for manipulating searches) to be literally searched for and found in the input string. Escaping depends on context, therefore this example does not cover string or delimiter escaping. Backslashes Saying that backsla...

Many languages allow regex to be enclosed or delimited between a couple of specific characters, usually the forward slash /. Delimiters have an impact on escaping: if the delimiter is / and the regex needs to look for / literals, then the forward slash must be escaped before it can be a literal (\/...

The easiest and quickest way to encode a Haskell data type to JSON with Aeson is using generics. {-# LANGUAGE DeriveGeneric #-} import GHC.Generics import Data.Text import Data.Aeson import Data.ByteString.Lazy First let us create a data type Person: data Person = Person { firstName :...

Detailed instructions on excel-formula(s). There are many formulas that you can choose from. They are divided up into 7 different categories and are on the FORMULAS tab in Excel. The categories are: Financial Logical Text Date & Time Lookup & Reference Math & trig More Function...

You should not save props into state. It is considered an anti-pattern. For example: export default class MyComponent extends React.Component { constructor() { super(); this.state = { url: '' } this.onChange = this.onChange.bind(this); ...

Sometimes you doesn't want to simply replace or remove the string. Sometimes you want to extract and process matches. Here an example of how you manipulate matches. What is a match ? When a compatible substring is found for the entire regex in the string, the exec command produce a match. A match i...

Some regex engines (such as .NET) can handle context-free expressions, and will work it out. But that's not the case for most standard engines. And even if they do, you'll end up having a complex hard-to-read expression, whereas using a parsing library could make the job easier. How to find all p...

Because Regular Expressions can do a lot, it is tempting to use them for the simplest operations. But using a regex engine has a cost in memory and processor usage: you need to compile the expression, store the automaton in memory, initialize it and then feed it with the string to run it. And there...

If you want to extract something from a webpage (or any representation/programming language), a regex is the wrong tool for the task. You should instead use your language's libraries to achieve the task. If you want to read HTML, or XML, or JSON, just use the library that parses it properly and ser...

UserType belongs to many Users <-> Users have one UserType One way navigation property with required public class UserType { public int UserTypeId {get; set;} } public class User { public int UserId {get; set;} public int UserTypeId {get; set;} public virtual UserType...

By using the .HasKey() method, a set of properties can be explicitly configured as the composite primary key of the entity. using System.Data.Entity; // .. public class PersonContext : DbContext { // .. protected override void OnModelCreating(DbModelBuilder modelBuilder) {...

By using the .HasMaxLength() method, the maximum character count can be configured for a property. using System.Data.Entity; // .. public class PersonContext : DbContext { // .. protected override void OnModelCreating(DbModelBuilder modelBuilder) { // .. ...

By using the .IsRequired() method, properties can be specified as mandatory, which means that the column will have a NOT NULL constraint. using System.Data.Entity; // .. public class PersonContext : DbContext { // .. protected override void OnModelCreating(DbModelBuilder modelB...

There are two common ways to encode a POST request body: URL encoding (application/x-www-form-urlencoded) and form data (multipart/form-data). Much of the code is similar, but the way you construct the body data is different. Sending a request using URL encoding Be it you have a server for your s...

A pointer is declared much like any other variable, except an asterisk (*) is placed between the type and the name of the variable to denote it is a pointer. int *pointer; /* inside a function, pointer is uninitialized and doesn't point to any valid object yet */ To declare two pointer variables...

The POSIX and C standards explicitly state that using fflush on an input stream is undefined behavior. The fflush is defined only for output streams. #include <stdio.h> int main() { int i; char input[4096]; scanf("%i", &i); fflush(stdin); // <-- unde...

Using alarm, user can schedule SIGALARM signal to be raised after specified interval. In case user did not blocked, ignored or specified explicit signal handler for this signal, the default action for this signal will be performed on arrival. Per specification default action for SIGALARM is to termi...