Tutorial by Examples: ha

Creating a hash table

Hash tables are created by make-hash-table: (defvar *my-table* (make-hash-table)) The function may take keyword parameters to further specify the behavior of the resulting hash table: test: Selects the function used to compare keys for equality. Maybe a designator for one of the functions eq,...

common-lisp • Hash tables

Iterating over the entries of a hash table with maphash

(defun print-entry (key value) (format t "~A => ~A~%" key value)) (maphash #'print-entry *my-table*) ;; => NIL Using maphash allows to iterate over the entries of a hash table. The order of iteration is unspecified. The first argument is a function accepting two parameters: ...

common-lisp • Hash tables

What are slots?

Slots offer a convenient way of distributing content from a parent component to a child component. This content can be anything from text, HTML or even other components. It can be helpful sometimes to think of slots as a means of injecting content directly into a child component's template. Slots ...

Vue.js • Slots

Newline character is not consumed in typical scanf() call

When this program #include <stdio.h> #include <string.h> int main(void) { int num = 0; char str[128], *lf; scanf("%d", &num); fgets(str, sizeof(str), stdin); if ((lf = strchr(str, '\n')) != NULL) *lf = '\0'; printf("%d \"%s\&...

C Language • Common pitfalls

Minimal Chart Example

Depending on the version of Chart.JS you are using (the current one being 2.X), the syntax is different to create a minimal example of a bar chart (JSFiddle Demo for 2.X). Chart.js 2.X <html> <body> <canvas id="myChart" width="400" height="400&...

chart.js • Getting started with chart.js

Adding/Removing an Observer with a Block

Instead of adding an observer with a selector, a block can be used: id testObserver = [[NSNotificationCenter defaultCenter] addObserverForName:@"TestNotification" object:nil ...

iOS • NSNotificationCenter

has_secure_token

Create User Model # Schema: User(token:string, auth_token:string) class User < ActiveRecord::Base has_secure_token has_secure_token :auth_token end Now when you create a new user a token and auth_token are automatically generated user = User.new user.save user.token # => "p...

Ruby on Rails • User Authentication in Rails

What is POSIX?

POSIX stands for "Portable Operating System Interface" and defines a set of standards to provide compatibility between different computing platforms. The current version of the standard is IEEE 1003.1 2016 and can be accessed from the OpenGroup POSIX specification. Previous versions incl...

POSIX • Getting started with POSIX

Assigning signals to a channel

Often times you will have reason to catch when your program is being told to stop by the OS and take some actions to preserve the state, or clean up your application. To accomplish this you can use the os/signal package from the standard library. Below is a simple example of assigning all signals fr...

Go • OS Signals

How to use a makefile other than Android.mk

ndk-build NDK_PROJECT_PATH=PROJECT_PATH APP_BUILD_SCRIPT=MyAndroid.mk

Android • Android NDK

Shake Detector in Android Example

public class ShakeDetector implements SensorEventListener { private static final float SHAKE_THRESHOLD_GRAVITY = 2.7F; private static final int SHAKE_SLOP_TIME_MS = 500; private static final int SHAKE_COUNT_RESET_TIME_MS = 3000; private OnShakeListener mListener; pri...

Android • Detect Shake Event in Android

Initial Setup with Android Studio

To setup for using Android Gradle Plugin you need many things: java gradle the Android project folder structure an Android Manifest initial plugin setup The easiest way to get all of them is to follow these steps: Donwload and Install Java OpenJDK version 6 or 7 (you can use 8 with addi...

android-gradle • Getting started with android-gradle

Message handling on Android

@Override public void onMessageReceived(RemoteMessage remoteMessage) { // ... // TODO(developer): Handle FCM messages here. Log.d(TAG, "From: " + remoteMessage.getFrom()); // Check if message contains a data payload. if (remoteMessage.getData().size() > 0) ...

firebase-cloud-messaging • Handling Message Notifications

Message handling on iOS

- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo fetchCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler { // If you are receiving a notification message while your app is in the background, // this callback will no...

firebase-cloud-messaging • Handling Message Notifications

D3js with Angular

Using D3js with Angular can open up new fronts of possibilities such as live updation of charts as soon as data is updated. We can encapsulate complete chart functionality within an Angular directive, which makes it easily reusable. index.html >> <!DOCTYPE html> <html ng-app="...

d3.js • Using D3 with other frameworks

What is a macro?

A macro is a series of keystrokes meant to be "played back" by Vim without any delay. Macros can be stored in registers or variables, bound to keys, or executed on the command line. Here is a simple macro that uppercases the third word on a line: 0wwgUiw That macro could be recorded i...

vim • Macros

Create an SKScene that Fills the SKView

A simple use case it to create an SKScene that exactly fills the SKView. This avoids the need to consider scaling the view to fit or setting a camera to show a part of the scene. The following code assumes an SKView called skView already exists (e.g. as defined in Create a Full Screen SKView using ...

sprite-kit • SKScene

Create an SKScene that Scales to fit the SKView

An SKScene has a scaleMode parameter that defines how it will change its size to fit within the SKView it is presented into the SKView if it is not the same size and/or shape. There are four options for scaleMode: AspectFit: the scene is scaled (but not stretched) until it fits within the view. ...

sprite-kit • SKScene

Create an SKScene with an SKCameraNode (iOS 9 and later)

You can place an SKCameraNode into an SKScene to define which part of the scene is shown in the SKView. Think of the SKScene as a 2D world with a camera floating above it: the SKView will show what the camera 'sees'. E.g. the camera could be attached to the main character's sprite to follow the act...

sprite-kit • SKScene

Chaining assignments in var declarations.

Chaining assignments as part of a var declaration will create global variables unintentionally. For example: (function foo() { var a = b = 0; })() console.log('a: ' + a); console.log('b: ' + b); Will result in: Uncaught ReferenceError: a is not defined 'b: 0' In the above examp...

JavaScript • Anti-patterns