Tutorial by Examples: r

Creating a CAGradientLayer

// View to hold the CAGradientLayer. let view: UIView = UIView(frame: CGRect(x: 0, y: 0, width: 320, height: 320)) // Initialize gradient layer. let gradientLayer: CAGradientLayer = CAGradientLayer() // Set frame of gradient layer. gradientLayer.frame = view.bounds // Color at...

iOS • CAGradientLayer

Create cryptographically secure random numbers

By default the Python random module use the Mersenne Twister PRNG to generate random numbers, which, although suitable in domains like simulations, fails to meet security requirements in more demanding environments. In order to create a cryptographically secure pseudorandom number, one can use Syst...

Python Language • Random module

Simple Bar Chart

index.html <!doctype html> <html> <head> <title>D3 Sample</title> </head> <body>  <div id=...

d3.js • Getting started with d3.js

Restarting docker container

docker restart <container> [<container>...] Option --time : Seconds to wait for stop before killing the container (default 10) docker restart <container> --time 10

Docker • Managing containers

Lazy, thread-safe Singleton (using Double Checked Locking)

This thread-safe version of a singleton was necessary in the early versions of .NET where static initialization was not guaranteed to be thread-safe. In more modern versions of the framework a statically initialized singleton is usually preferred because it is very easy to make implementation mistak...

C# Language • Singleton Implementation

Concerns

To avoid repetition in nested routes, concerns provide a great way of sharing common resources that are reusable. To create a concern use the method concern within the routes.rb file. The method expects a symbol and block: concern :commentable do resources :comments end While not creating a...

Ruby on Rails • Routing

List all contributions grouped by author name

git shortlog summarizes git log and groups by author If no parameters are given, a list of all commits made per committer will be shown in chronological order. $ git shortlog Committer 1 (<number_of_commits>): Commit Message 1 Commit Message 2 ... Committer 2 (<number_of_...

Git • Browsing the history

Loop control with break, next, and redo

The flow of execution of a Ruby block may be controlled with the break, next, and redo statements. break The break statement will exit the block immediately. Any remaining instructions in the block will be skipped, and the iteration will end: actions = %w(run jump swim exit macarena) index = 0 ...

Ruby Language • Control Flow

Underlying references of named method delegates

When assigning named methods to delegates, they will refer to the same underlying object if: They are the same instance method, on the same instance of a class They are the same static method on a class public class Greeter { public void WriteInstance() { Console.Write...

C# Language • Delegates

Declaring a delegate type

The following syntax creates a delegate type with name NumberInOutDelegate, representing a method which takes an int and returns an int. public delegate int NumberInOutDelegate(int input); This can be used as follows: public static class Program { static void Main() { Number...

C# Language • Delegates

The Func, Action and Predicate delegate types

The System namespace contains Func<..., TResult> delegate types with between 0 and 15 generic parameters, returning type TResult. private void UseFunc(Func<string> func) { string output = func(); // Func with a single generic type parameter returns that type Console.WriteLine...

C# Language • Delegates

Closure

Closures in Python are created by function calls. Here, the call to makeInc creates a binding for x that is referenced inside the function inc. Each call to makeInc creates a new instance of this function, but each instance has a link to a different binding of x. def makeInc(x): def inc(y): ...

Python Language • Functions

Running your script

On either Linux/UNIX or Windows, a script can be passed as an argument to the PHP executable, with that script's options and arguments following: php ~/example.php foo bar c:\php\php.exe c:\example.php foo bar This passes foo and bar as arguments to example.php. On Linux/UNIX, the preferred me...

PHP • Command Line Interface (CLI)

hasattr function bug in Python 2

In Python 2, when a property raise a error, hasattr will ignore this property, returning False. class A(object): @property def get(self): raise IOError class B(object): @property def get(self): return 'get in b' a = A() b = B() print 'a hasattr get:...

Python Language • Incompatibilities moving from Python 2 to Python 3

Univariate Geometric Brownian Motion

The dynamics of the Geometric Brownian Motion (GBM) are described by the following stochastic differential equation (SDE): I can use the exact solution to the SDE to generate paths that follow a GBM. Given daily parameters for a year-long simulation mu = 0.08/250; sigma = 0.25/sqrt(...

MATLAB Language • Financial Applications

Passing in Arrays to Functions

int getListOfFriends(size_t size, int friend_indexes[]) { size_t i = 0; for (; i < size; i++) { friend_indexes[i] = i; } } C99C11 /* Type "void" and VLAs ("int friend_indexes[static size]") require C99 at least. In C11 VLAs are optional. */ void getLis...

C Language • Function Parameters

Installation or Setup

Leiningen Note: If you're going to use Leiningen, you first need to download and install JDK 6 or newer. The easiest way to get started with Clojure is to download and install Leiningen, the de facto standard tool to manage Clojure projects. Linux: curl https://raw.githubusercontent.com/technoma...

clojurescript • Getting started with clojurescript

Adjust workspace to your needs and freely navigate it

One of the things that can really boost your productivity while writing the code is effectively navigating the workspace. This also means making it comfortable for the moment. It's possible to achieve this by adjusting which areas of workspaces you see. The buttons on the top of the navigation and ...

Xcode • Projects & Workspaces

Stream output to client

/** * Enables output buffer streaming. Calling this function * immediately flushes the buffer to the client, and any * subsequent output will be sent directly to the client. */ function _stream() { ob_implicit_flush(true); ob_end_flush(); }

PHP • Output Buffering

Fedora Installation

dnf install erlang elixir

Elixir Language • Installation