Tutorial by Examples: an

Use requestAnimationFrame() NOT setInterval() for animation loops

requestAnimationFrame is similar to setInterval, it but has these important improvements: The animation code is synchronized with display refreshes for efficiency The clear + redraw code is scheduled, but not immediately executed. The browser will execute the clear + redraw code only when the d...

html5-canvas • Animation

Animate an image across the Canvas

This example loads and animates and image across the Canvas Important Hint! Make sure you give your image time to fully load by using image.onload. Annotated Code <!doctype html> <html> <head> <style> body{ background-color:white; } #canvas{border:1px solid re...

html5-canvas • Animation

Don't draw animations in your event handlers (a simple sketch app)

During mousemove you get flooded with 30 mouse events per second. You might not be able to redraw your drawings at 30 times per second. Even if you can, you're probably wasting computing power by drawing when the browser is not ready to draw (wasted == across display refresh cycles). Therefore it m...

html5-canvas • Animation

UIColor from an image pattern

You can create a UIColor object using an image pattern by using the UIColor(patternImage:_) method. btn.backgroundColor = UIColor(patternImage: UIImage(named: "image")!)

iOS • UIColor

Even and Odd Numbers

The even? method can be used to determine if a number is even 4.even? # => true 5.even? # => false The odd? method can be used to determine if a number is odd 4.odd? # => false 5.odd? # => true

Ruby Language • Numbers

Restrict Number to Min/Max Range

If you need to clamp a number to keep it inside a specific range boundary function clamp(min, max, val) { return Math.min(Math.max(min, +val), max); } console.log(clamp(-10, 10, "4.30")); // 4.3 console.log(clamp(-10, 10, -8)); // -8 console.log(clamp(-10, 10, 12)); // ...

JavaScript • Arithmetic (Math)

Dialects of Lisp and their implementations

Invented by John McCarthy around 1958, Lisp (List Processor) has continued to grow into an entire family of languages. Since StackOverflow is more about practical programming problems, typically problems will involve actual Lisp dialects or derived languages and their implementations. Problems that...

lisp • Getting started with lisp

Go Clean

go clean will clean up any temporary files created when invoking go build on a program. It will also clean files left over from Makefiles.

Go • The Go Command

Panic

A panic halts normal execution flow and exits the current function. Any deferred calls will then be executed before control is passed to the next higher function on the stack. Each stack's function will exit and run deferred calls until the panic is handled using a deferred recover(), or until the...

Go • Panic and Recover

GroupBy Sum and Count

Let's take a sample class: public class Transaction { public string Category { get; set; } public DateTime Date { get; set; } public decimal Amount { get; set; } } Now, let us consider a list of transactions: var transactions = new List<Transaction> { new Transaction...

C# Language • LINQ Queries

Creating a custom analyzer

Most analysis customization is in the createComponents class, where the Tokenizer and TokenFilters are defined. CharFilters can be added in the initReader method. Analyzer analyzer = new Analyzer() { @Override protected Reader initReader(String fieldName, Reader reader) { retu...

lucene • Analysis

Iterating manually through analyzed tokens

TokenStream stream = myAnalyzer.tokenStream("myField", textToAnalyze); stream.addAttribute(CharTermAttribute.class); stream.reset(); while(stream.incrementToken()) { CharTermAttribute token = stream.getAttribute(CharTermAttribute.class); System.out.println(token.toString()); ...

lucene • Analysis

Get an ISO 8601 timestamp

Without timezone, with microseconds from datetime import datetime datetime.now().isoformat() # Out: '2016-07-31T23:08:20.886783' With timezone, with microseconds from datetime import datetime from dateutil.tz import tzlocal datetime.now(tzlocal()).isoformat() # Out: '2016-07-31T23:09:4...

Python Language • Date and Time

Right shift of a negative integer

int signed_integer = -1; // The right shift operation exhibits implementation-defined behavior: int result = signed_integer >> 1;

C Language • Implementation-defined behaviour

Assigning an out-of-range value to an integer

// Supposing SCHAR_MAX, the maximum value that can be represented by a signed char, is // 127, the behavior of this assignment is implementation-defined: signed char integer; integer = 128;

C Language • Implementation-defined behaviour

Master and Detail View interaction using Delegates in Objective C

UISplitViewController must be the rootViewController of your application. AppDelegate.m - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { // Override point for customization after application launch. self.window = [[UIWindow alloc] i...

iOS • UISplitViewController

Accessing a dangling reference

It is illegal to access a reference to an object that has gone out of scope or been otherwise destroyed. Such a reference is said to be dangling since it no longer refers to a valid object. #include <iostream> int& getX() { int x = 42; return x; } int main() { int& r...

C++ • Undefined Behavior

Creating a Pair and accessing the elements

Pair allows us to treat two objects as one object. Pairs can be easily constructed with the help of template function std::make_pair. Alternative way is to create pair and assign its elements (first and second) later. #include <iostream> #include <utility> int main() { std::p...

C++ • std::pair

Removing unwanted characters from a string

The example Checking a string for unwanted characters, describes how to test and reject strings that don't meet certain criteria. Obviously, rejecting input outright is not always possible, and sometimes you just have to make do with what you receive. In these cases, a cautious developer will attemp...

guava • Strings

The ANSI Common Lisp standard in Texinfo format (especially useful for GNU Emacs)

GNU Emacs uses a special format for documentation: info. The Common Lisp standard has been converted to the Texinfo format, which can be used to create documentation browsable with the info reader in GNU Emacs. See here: dpans2texi.el converts the TeX sources of the draft ANSI Common Lisp standard...

common-lisp • ANSI Common Lisp, the language standard and its documentation