Tutorial by Examples: r

Method overriding is the ability of subtypes to redefine (override) the behavior of their supertypes. In Java, this translates to subclasses overriding the methods defined in the super class. In Java, all non-primitive variables are actually references, which are akin to pointers to the location of...

Objective-C CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"position.x"]; animation.fromValue = @0; animation.toValue = @320; animation.duration = 1; [_label.layer addAnimation:animation forKey:@"basic"]; Swift let animation = CAB...

CGRect boundingRect = CGRectMake(-150, -150, 300, 300); CAKeyframeAnimation *orbit = [CAKeyframeAnimation animation]; orbit.keyPath = @"position"; orbit.path = CFAutorelease(CGPathCreateWithEllipseInRect(boundingRect, NULL)); orbit.duration = 4; orbit.additive = YES; orbit.repeatC...

use Data::Dumper; my $data_structure = { foo => 'bar' }; print Dumper $data_structure; Using Data::Dumper is an easy way to look at data structures or variable content at run time. It ships with Perl and you can load it easily. The Dumper function returns the data structure serialized in a...

Step 1 If you already have Django installed, you can skip this step. pip install Django Step 2 Create a new project django-admin startproject hello That will create a folder named hello which will contain the following files: hello/ ├── hello/ │ ├── __init__.py │ ├── settings.py │...

The docker rmi command is used to remove images: docker rmi <image name> The full image name must be used to remove an image. Unless the image has been tagged to remove the registry name, it needs to be specified. For example: docker rmi registry.example.com/username/myAppImage:1.3.5 I...

Although not strictly required, it is highly recommended to start your project in a "virtual environment." A virtual environment is a container (a directory) that holds a specific version of Python and a set of modules (dependencies), and which does not interfere with the operating system'...

Detailed instructions on getting emacs set up or installed. Official instructions are available on the GNU Emacs website. Debian systems On systems with the Debian package manager (such as Debian, Ubuntu, and Mint) Emacs can be installed via the simple command: sudo apt-get install emacs For ...

Tkinter comes pre-installed with the Python installer binaries for Mac OS X and the Windows platform. So if you install Python from the official binaries for Mac OS X or Windows platform, you are good to go with Tkinter. For Debian versions of Linux you have to install it manually by using the foll...

Often, we need to perform an operation over every element in a variadic template parameter pack. There are many ways to do this, and the solutions get easier to read and write with C++17. Suppose we simply want to print every element in a pack. The simplest solution is to recurse: C++11 void print...

An XML document is a text file that conforms to the XML specification's well-formedness rules. Such a conforming document is said to be well-formed (not to be confused with valid). XML is very strict with well-formedness in comparison to other languages such as HTML. A text file that is not well-for...

The internal keyword makes a class (including nested classes), property, method or field available to every consumer in the same assembly: internal class Foo { internal string SomeProperty {get; set;} } internal class Bar { var myInstance = new Foo(); internal string SomeField ...

docker run --restart=always -d <container> By default, Docker will not restart containers when the Docker daemon restarts, for example after a host system reboot. Docker provides a restart policy for your containers by supplying the --restart command line option. Supplying --restart=always ...

Const ForReading = 1 Const ForWriting = 2 Const ForAppending = 8 Sub FsoExample() Dim fso As Object ' declare variable Set fso = CreateObject("Scripting.FileSystemObject") ' Set it to be a File System Object ' now use it to check if a file exists Dim myFilePath A...

Const ForReading = 1 Const ForWriting = 2 Const ForAppending = 8 Sub ReadTextFileExample() Dim fso As Object Set fso = CreateObject("Scripting.FileSystemObject") Dim sourceFile As Object Dim myFilePath As String Dim myFileText As String myFilePath = &...

Sub CreateTextFileExample() Dim fso As Object Set fso = CreateObject("Scripting.FileSystemObject") Dim targetFile As Object Dim myFilePath As String Dim myFileText As String myFilePath = "C:\mypath\to\myfile.txt" Set targetFile = fso.CreateT...

Const ForReading = 1 Const ForWriting = 2 Const ForAppending = 8 Sub WriteTextFileExample() Dim oFso Set oFso = CreateObject("Scripting.FileSystemObject") Dim oFile as Object Dim myFilePath as String Dim myFileText as String myFilePath = "C:\my...

traverse_ executes an Applicative action for every element in a Foldable structure. It ignores the action's result, keeping only the side-effects. (For a version which doesn't discard results, use Traversable.) -- using the Writer applicative functor (and the Sum monoid) ghci> runWriter $ trave...

The ternary operator is used for inline conditional expressions. It is best used in simple, concise operations that are easily read. The order of the arguments is different from many other languages (such as C, Ruby, Java, etc.), which may lead to bugs when people unfamiliar with Python's "s...

JavaScript will try to automatically convert variables to more appropriate types upon use. It's usually advised to do conversions explicitly (see other examples), but it's still worth knowing what conversions take place implicitly. "1" + 5 === "15" // 5 got converted to string. ...