Tutorial by Examples: r

Specific to Windows System and android Phone: Requirements: USB Cable Android Device Android Driver Software Basically after connecting USB cable PC detects the Android Device and it will automatically search for the required Drivers for that Android Device. If that drivers are not found th...

Removing duplicate values in a list can be done by converting the list to a set (that is an unordered collection of distinct objects). If a list data structure is needed, then the set can be converted back to a list using the function list(): names = ["aixk", "duke", "edik&...

A closure is the PHP equivalent of an anonymous function, eg. a function that does not have a name. Even if that is technically not correct, the behavior of a closure remains the same as a function's, with a few extra features. A closure is nothing but an object of the Closure class which is create...

It is possible, inside a closure, to use an external variable with the special keyword use. For instance: <?php $quantity = 1; $calculator = function($number) use($quantity) { return $number + $quantity; }; var_dump($calculator(2)); // Shows "3" You can go further by ...

As seen previously, a closure is nothing but an instance of the Closure class, and different methods can be invoked on them. One of them is bindTo, which, given a closure, will return a new one that is bound to a given object. For example: <?php $myClosure = function() { echo $this->p...

Let's consider this example: <?php $myClosure = function() { echo $this->property; }; class MyClass { public $property; public function __construct($propertyValue) { $this->property = $propertyValue; } } $myInstance = new MyClass('Hello world...

Since PHP7, it is possible to bind a closure just for one call, thanks to the call method. For instance: <?php class MyClass { private $property; public function __construct($propertyValue) { $this->property = $propertyValue; } } $myClosure = function() ...

In general, an observer is a class with a specific method being called when an action on the observed object occurs. In certain situations, closures can be enough to implement the observer design pattern. Here is a detailed example of such an implementation. Let's first declare a class whose purpos...

We define two sets a and b >>> a = {1, 2, 2, 3, 4} >>> b = {3, 3, 4, 4, 5} NOTE: {1} creates a set of one element, but {} creates an empty dict. The correct way to create an empty set is set(). Intersection a.intersection(b) returns a new set with elements present in bot...

Even though Python natively supports big integers, taking the nth root of very large numbers can fail in Python. x = 2 ** 100 cube = x ** 3 root = cube ** (1.0 / 3) OverflowError: long int too large to convert to float When dealing with such large integers, you will need to use a custom f...

A git repository is an on-disk data structure which stores metadata for a set of files and directories. It lives in your project's .git/ folder. Every time you commit data to git, it gets stored here. Inversely, .git/ contains every single commit. It's basic structure is like this: .git/ obj...

HEAD is a special ref. It always points to the current object. You can see where it's currently pointing by checking the .git/HEAD file. Normally, HEAD points to another ref: $cat .git/HEAD ref: refs/heads/mainline But it can also point directly to an object: $ cat .git/HEAD 4bb6f98a223abc...

A ref is essentially a pointer. It's a name that points to an object. For example, "master" --> 1a410e... They are stored in `.git/refs/heads/ in plain text files. $ cat .git/refs/heads/mainline 4bb6f98a223abc9345a0cef9200562333 This is commonly what are called branches. Howeve...

A tree basically represents a folder in a traditional filesystem: nested containers for files or other folders. A tree contains: 0 or more blob objects 0 or more tree objects Just as you can use ls or dir to list the contents of a folder, you can list the contents of a tree object. $ git ca...

The git commit command does a few things: Create blobs and trees to represent your project directory - stored in .git/objects Creates a new commit object with your author information, commit message, and the root tree from step 1 - also stored in .git/objects Updates the HEAD ref in .git/HEAD t...

Running git reset --hard moves refs to the specified hash/ref. Moving MyBranch to b8dc53: $ git checkout MyBranch # moves HEAD to MyBranch $ git reset --hard b8dc53 # makes MyBranch point to b8dc53

Running git checkout -b <refname> will create a new ref that points to the current commit. $ cat .git/head 1f324a $ git checkout -b TestBranch $ cat .git/refs/heads/TestBranch 1f324a

The non-block do construct looks like integer i do 100, i=1, 5 100 print *, i That is, where the labelled termination statement is not a continue statement. There are various restrictions on the statement that can be used as the termination statement and the whole thing is generally v...

Common Lisp already has a reverse function, but if it didn't, then it could be implemented easily using reduce. Given a list like (1 2 3) === (cons 1 (cons 2 (cons 3 '()))) the reversed list is (cons 3 (cons 2 (cons 1 '()))) === (3 2 1) That may not be an obvious use of reduce, but if we ha...

To verify that nvm has been installed, do: command -v nvm which should output 'nvm' if the installation was successful.