Tutorial by Examples: p

DispatchSemaphore provides an efficient implementation of a traditional counting semaphore, which can be used to control access to a resource across multiple execution contexts. A scenario for when to use a semaphore could be if you are doing some file reading/writing, if multiple tasks are t...

Swift 3 Serial Queue func serialQueues () { let serialQueue = DispatchQueue(label: "com.example.serial") //default queue type is a serial queue let start = Date () for i in 0...3 { //launch a bunch of tasks serialQueue.a...

This example echoes the special character ! into a file. This would only work when DelayedExpansion is disabled. When delayed expansion in enabled, you will need to use three carets and an exclamation mark like this: @echo off setlocal enabledelayedexpansion echo ^^^!>file echo ^>>&...

Redis supplies the SISMEMBER command to test if a particular item is already a member of a set. Using the SISMEMBER command I can test and see if apple is already a member of my fruit set. If I construct my fruit set from the previous example, I can check and see if it contains apple using the fol...

Redis provides seven different operations for working with scripts: Eval operations (EVAL, EVALSHA) SCRIPT operations (DEBUG, EXISTS, FLUSH, KILL, LOAD) The EVAL command evaluates a script provided as a string argument to the server. Scripts can access the specified Redis keys named as argum...

Be aware that the WebBrowser control is not sympathetic to your XAML definition, and renders itself over the top of other things. For example, if you put it inside a BusyIndicator that has been marked as being busy, it will still render itself over the top of that control. The solution is to bind th...

Since we have many different algorithms to choose from, when we want to sort an array, we need to know which one will do it's job. So we need some method of measuring algoritm's speed and reliability. That's where Asymptotic analysis kicks in. Asymptotic analysis is the process of describing the ef...

Quicksort is one of the advanced algorithms. It features a time complexity of O(n log n) and applies a divide & conquer strategy. This combination results in advanced algorithmic performance. Quicksort first divides a large array into two smaller sub-arrays: the low elements and the high element...

g + geom_bar(aes(x = cut, fill = color), position = "fill") + guides(fill = guide_legend(title = NULL))

g + geom_bar(mapping = aes(x = cut, fill = clarity), position = "dodge") + theme(axis.text = element_text(colour = "red", size = 12))

let messageBox:MessageBox = MessageBox() // set messageBox.setObject("TestObject1", forKey:"TestKey1") // get // but don't remove it, keep it stored, so that it can still be retrieved later let someObject:String = messageBox.getObject(forKey:"TestKey1", remov...

// init mUIPheonix = UIPheonix(with:myCollectionView) mUIPheonix = UIPheonix(with:myTableView) // connect model-view mUIPheonix.setModelViewRelationships([MyModel.nameOfClass:MyView.nameOfClass]) // add models for the UI models.append(SimpleButtonModel(id:1, title:"Hello World!")...

We show a plot similar to the showed at Linear regression on the mtcars dataset. First with defaults and the with some customization of the parameters. #help("mtcars") fit <- lm(mpg ~ wt, data = mtcars) bs <- round(coef(fit), 3) lmlab <- paste0("mpg = ", bs[1], ...

How to ... 1 - use twig extension class that extends use \Twig_Extension class dobToAge extends \Twig_Extension { 2 - Add the appropriate filter by overriding getFilters() method public function getFilters() { return array( 'age' => new \Twig_Filter_Method($this, '...

If you need to select between several options, enabling just one via enable_if<> can be quite cumbersome, since several conditions needs to be negated too. The ordering between overloads can instead be selected using inheritance, i.e. tag dispatch. Instead of testing for the thing that ne...

This is the typical approach for novice developers building SQL action queries. They are vulnerable to the Bobby Tables type SQL Injection attacks. Dim strSQL As String strSQL = "INSERT INTO Employees chrFirstName, chrLastName, chrPhone " _ & "VALUES ('" & M...

This approach will prevent a user from embedding a second SQL statement in their input for execution. Dim strSQL As String Dim db As DAO.Database Dim qdf As DAO.QueryDef strSQL = "PARAMETERS [FirstName] Text(255), [LastName] Text(255), [Phone] Text(255); " _ & "INS...

// create the dictionary that will be sent to the blocks var myDictionary:Dictionary<String, Any> = Dictionary<String, Any>() myDictionary["InitialKey"] = "InitialValue" // create block queue let myBlockQueue:MKBlockQueue = MKBlockQueue() // block 1 let b1...

Detailed instructions on getting opengl-es-2.0 set up or installed.