Tutorial by Examples: io

C-h f runs the function describe-function, which displays information on the usage and purpose of a given function. This is especially useful for functions that do not have a mapped key binding that can be used for documentation lookup via C-h k.

Another powerful & mature concurrency tool in Haskell is Software Transactional Memory, which allows for multiple threads to write to a single variable of type TVar a in an atomic manner. TVar a is the main type associated with the STM monad and stands for transactional variable. They're used m...

Intersection of Hashes To get the intersection of two hashes, return the shared keys the values of which are equal: hash1 = { :a => 1, :b => 2 } hash2 = { :b => 2, :c => 3 } hash1.select { |k, v| (hash2.include?(k) && hash2[k] == v) } # => { :b => 2 } Union (...

Synopsis A fully functional demo of Firebase v3 Web authentication viewable here. Sign in with Facebook, Github, Google, Twitter, password based, and anonymous accounts. The code, available on Github, is easy to read and follow and is well documented. The focus is on the fully functional authent...

Here is a quick reference for advanced insertion, formatting, and filtering commands/shortcuts. Command/ShortcutResultg + ? + mPerform rot13 encoding, on movement mn + ctrl + a+n to number under cursorn + ctrl + x-n to number under cursorg + q+ mFormat lines of movement m to fixed width:rce wCenter...

When your app crashes, Xcode will enter the debugger and show you more information about the crash: The most important parts are: The red arrow The red arrow displays which line of code crashed & why it crashed. The debugger console Many crashes log more information to the debugger consol...

A SIGABRT or an EXC_BAD_INSTRUCTION usually means the app crashed itself intentionally because some check failed. These should log a message to the debugger console with more information; check there for more information. Many SIGABRTs are caused by uncaught Objective-C exceptions. There are a lo...

The following example shows how to set up Dependency Injection using Ninject as an IoC container. First add a CustomModule class to your WebJob project, and add any dependency bindings there. public class CustomModule : NinjectModule { public override void Load() { Bind<IMyI...

Mixins are similar to defining and calling functions. Say, if we need to create a repetitive style, mixins are handy. Mixins may or may not take parameters. For e.g.: .default-round-borders { border-radius: 5px; -moz-border-radius: 5px; -webkit-border-radius: 5px; } .round-b...

In Less, unlike Sass or Shell, the variables are declared by having names starting with a @ symbol. For example: @sky-blue: #87ceeb; body { background-color: @sky-blue; } The above example gives you: body { background-color: #87ceeb; } Here it explains how to declare a variable an...

Consider the following example: @sky-blue: #87ceeb; @dark-sky-blue: @sky-blue + #333; body { background-color: @dark-sky-blue; } The above example gives you: body { background-color: #baffff; } Here it explains how to declare a variable and also make operations on a particular va...

C++11 The std::is_same<T, T> type relation is used to compare two types. It will evaluate as boolean, true if the types are the same and false if otherwise. e.g. // Prints true on most x86 and x86_64 compilers. std::cout << std::is_same<int, int32_t>::value << "\n&qu...

aiohttp provides asynchronous websockets. Python 3.x3.5 import asyncio from aiohttp import ClientSession with ClientSession() as session: async def hello_world(): websocket = await session.ws_connect("wss://echo.websocket.org") websocket.send_str("Hell...

aiohttp.ClientSession may be used as a parent for a custom WebSocket class. Python 3.x3.5 import asyncio from aiohttp import ClientSession class EchoWebSocket(ClientSession): URL = "wss://echo.websocket.org" def __init__(self): super().__init__() self....

By default, npm installs the latest available version of modules according to each dependencies' semantic version. This can be problematic if a module author doesn't adhere to semver and introduces breaking changes in a module update, for example. To lock down each dependencies' version (and the ve...

Mockito.when(mock.returnSomething()).thenReturn("my val"); mock.returnSomething(); // returns "my val" mock.returnSomething(); // returns "my val" again mock.returnSomething(); // returns "my val" again and again and again... If you want different valu...

Firstly you have to add Xamarin.Android.Support.V7.AppCompat library for NuGet: https://www.nuget.org/packages/Xamarin.Android.Support.v7.AppCompat/ In the "values" folder under "Resources" add new xml file called "styles.xml": "styles.xml" file should co...

Java release naming is a little confusing. There are actually two systems of naming and numbering, as shown in this table: JDK versionMarketing namejdk-1.0JDK 1.0jdk-1.1JDK 1.1jdk-1.2J2SE 1.2......jdk-1.5J2SE 1.5 rebranded Java SE 5jdk-1.6Java SE 6jdk-1.7Java SE 7jdk-1.8Java SE 8jdk-91Java SE 9 (n...

In most cases all data that is accessed by several threads should be initialized before the threads are created. This ensures that all threads start with a clear state and no race condition occurs. If this is not possible once_flag and call_once can be used #include <threads.h> #include &lt...

Function composition allows for two functions to operate and be viewed as a single function. Expressed in mathematical terms, given a function f(x) and a function g(x), the function h(x) = f(g(x)). When a function is compiled, it is compiled to a type related to Function1. Scala provides two method...