Tutorial by Examples: a

Simple Bar Chart

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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

Statically Initialized Singleton

public class Singleton { private readonly static Singleton instance = new Singleton(); private Singleton() { } public static Singleton Instance => instance; } This implementation is thread-safe because in this case instance object is initialized in the static constructor. The ...

C# Language • Singleton Implementation

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

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

Assigning a named method to a delegate

Named methods can be assigned to delegates with matching signatures: public static class Example { public static int AddOne(int input) { return input + 1; } } Func<int,int> addOne = Example.AddOne Example.AddOne takes an int and returns an int, its signature ...

C# Language • Delegates

Delegate Equality

Calling .Equals() on a delegate compares by reference equality: Action action1 = () => Console.WriteLine("Hello delegates"); Action action2 = () => Console.WriteLine("Hello delegates"); Action action1Again = action1; Console.WriteLine(action1.Equals(action1)) // True ...

C# Language • Delegates

Assigning to a delegate by lambda

Lambdas can be used to create anonymous methods to assign to a delegate: Func<int,int> addOne = x => x+1; Note that the explicit declaration of type is required when creating a variable this way: var addOne = x => x+1; // Does not work

C# Language • Delegates

Case Class Equality

One feature provided for free by case classes is an auto-generated equals method that checks the value equality of all individual member fields instead of just checking the reference equality of the objects. With ordinary classes: class Foo(val i: Int) val a = new Foo(3) val b = new Foo(3) prin...

Scala Language • Case Classes

Type Casting

PHP will generally correctly guess the data type you intend to use from the context it's used in, however sometimes it is useful to manually force a type. This can be accomplished by prefixing the declaration with the name of the required type in parenthesis: $bool = true; var_dump($bool); // bool...

PHP • Types

exec statement is a function in Python 3

In Python 2, exec is a statement, with special syntax: exec code [in globals[, locals]]. In Python 3 exec is now a function: exec(code, [, globals[, locals]]), and the Python 2 syntax will raise a SyntaxError. As print was changed from statement into a function, a __future__ import was also added. ...

Python Language • Incompatibilities moving from Python 2 to Python 3

Conditional loop

The for keyword is also used for conditional loops, traditionally while loops in other programming languages. package main import ( "fmt" ) func main() { i := 0 for i < 3 { // Will repeat if condition is true i++ fmt.Println(i) } } play ...

Go • Loops

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