Tutorial by Examples: s

Value vs Handle classes

Classes in MATLAB are divided into two major categories: value classes and handle classes. The major difference is that when copying an instance of a value class, the underlying data is copied to the new instance, while for handle classes the new instance points to the original data and changing val...

Installation or Setup

Setup for Yii 1.1 Step 1 - downloading Yii Download the Yii framework bundle from the Yii website Inside the downloaded bundle there are 3 folders, namely: demos framework requirements demos, as the name suggests contains a number of demo Yii applications. framework contains the Yii framew...

Subquery in WHERE clause

Use a subquery to filter the result set. For example this will return all employees with a salary equal to the highest paid employee. SELECT * FROM Employees WHERE Salary = (SELECT MAX(Salary) FROM Employees)

Subquery in FROM clause

A subquery in a FROM clause acts similarly to a temporary table that is generated during the execution of a query and lost afterwards. SELECT Managers.Id, Employees.Salary FROM ( SELECT Id FROM Employees WHERE ManagerId IS NULL ) AS Managers JOIN Employees ON Managers.Id = Employees.Id ...

Subquery in SELECT clause

SELECT Id, FName, LName, (SELECT COUNT(*) FROM Cars WHERE Cars.CustomerId = Customers.Id) AS NumberOfCars FROM Customers

Parsing HTML from a string

PHP implements a DOM Level 2 compliant parser, allowing you to work with HTML using familiar methods like getElementById() or appendChild(). $html = '<html><body><span id="text">Hello, World!</span></body></html>'; $doc = new DOMDocument(); libxml_u...

Using XPath

$html = '<html><body><span class="text">Hello, World!</span></body></html>'; $doc = new DOMDocument(); $doc->loadHTML($html); $xpath = new DOMXPath($doc); $span = $xpath->query("//span[@class='text']")->item(0); echo $span-&...

Reading and writing to a file using ioutil

A simple program that writes "Hello, world!" to test.txt, reads back the data, and prints it out. Demonstrates simple file I/O operations. package main import ( "fmt" "io/ioutil" ) func main() { hello := []byte("Hello, world!") //...
Go • File I/O

Listing all the files and folders in the current directory

package main import ( "fmt" "io/ioutil" ) func main() { files, err := ioutil.ReadDir(".") if err != nil { panic(err) } fmt.Println("Files and folders in the current directory:") for _, fileInfo := range fi...
Go • File I/O

Accessing class members

To access member variables and member functions of an object of a class, the . operator is used: struct SomeStruct { int a; int b; void foo() {} }; SomeStruct var; // Accessing member variable a in var. std::cout << var.a << std::endl; // Assigning member variable b in v...

Creating a pure JSON table

To create a pure JSON table you need to provide a single field with the type JSONB: CREATE TABLE mytable (data JSONB NOT NULL); You should also create a basic index: CREATE INDEX mytable_idx ON mytable USING gin (data jsonb_path_ops); At this point you can insert data in to the table and que...

Querying complex JSON documents

Taking a complex JSON document in a table: CREATE TABLE mytable (data JSONB NOT NULL); CREATE INDEX mytable_idx ON mytable USING gin (data jsonb_path_ops); INSERT INTO mytable VALUES($$ { "name": "Alice", "emails": [ "[email protected]", ...

Installation of scikit-learn

The current stable version of scikit-learn requires: Python (>= 2.6 or >= 3.3), NumPy (>= 1.6.1), SciPy (>= 0.9). For most installation pip python package manager can install python and all of its dependencies: pip install scikit-learn However for linux systems it is recomm...

Installation or Setup

The D programming language's standard compiler DMD can run on all major platforms. To install DMD see here. To install by command line you may run the command (found on the D website): curl -fsS https://dlang.org/install.sh | bash -s dmd Package Managers Arch Linux pacman -S dlang Chocolate...

Formatted strings

Ruby can inject an array of values into a string by replacing any placeholders with the values from the supplied array. "Hello %s, my name is %s!" % ['World', 'br3nt'] # => Hello World, my name is br3nt! The place holders are represented by two %s and the values are supplied by the...

Repeat a String n times

Problem: Create a String containing n repetitions of a String s. The trivial approach would be repeatedly concatenating the String final int n = ... final String s = ... String result = ""; for (int i = 0; i < n; i++) { result += s; } This creates n new string instances ...

Installation or Setup

SWI-Prolog Windows and Mac: Download SWI-Prolog at the official website Simply install by following the installer instructions. Linux (PPA): Add the PPA ppa:swi-prolog/stable to your system’s software sources (developers may choose for ppa:swi-prolog/devel) : Open a terminal (Ctrl+...

Distinct

Returns unique values from an IEnumerable. Uniqueness is determined using the default equality comparer. int[] array = { 1, 2, 3, 4, 2, 5, 3, 1, 2 }; var distinct = array.Distinct(); // distinct = { 1, 2, 3, 4, 5 } To compare a custom data type, we need to implement the IEquatable<T> i...

Installation or Setup

If you don't have any RubyGems installed, there is still the pre-gem approach to getting software, doing it manually: Download from RubyGems Unpack into a directory and cd there Install with: ruby setup.rb (you may need admin/root privilege) sudo ruby setup.rb For more details...

Pattern Matching with Case Classes

Every case class defines an extractor that can be used to capture the members of the case class when pattern matching: case class Student(name: String, email: String) def matchStudent1(student: Student): String = student match { case Student(name, email) => s"$name has the following...

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