Tutorial by Examples: u

A std::vector can be useful for returning a dynamic number of variables of the same type. The following example uses int as data type, but a std::vector can hold any type that is trivially copyable: #include <vector> #include <iostream> // the following function returns all integers...

You can call a function in Racket by wrapping it in parentheses with the arguments after it. This looks like (function argument ...). > (define (f x) x) > (f 1) 1 > (f "salmon") "salmon" > (define (g x y) (string-append x y)) > (g "large" "sal...

A common pattern in C# is using bool TryParse(object input, out object value) to safely parse objects. The out var declaration is a simple feature to improve readability. It allows a variable to be declared at the same time that is it passed as an out parameter. A variable declared this way is sco...

Basics A tuple is an ordered, finite list of elements. Tuples are commonly used in programming as a means to work with one single entity collectively instead of individually working with each of the tuple's elements, and to represent individual rows (ie. "records") in a relational databa...

Local functions are defined within a method and aren't available outside of it. They have access to all local variables and support iterators, async/await and lambda syntax. This way, repetitions specific to a function can be functionalized without crowding the class. As a side effect, this improves...

Define AccumulatorParam import org.apache.spark.AccumulatorParam object StringAccumulator extends AccumulatorParam[String] { def zero(s: String): String = s def addInPlace(s1: String, s2: String)= s1 + s2 } Use: val accumulator = sc.accumulator("")(StringAccumulator) sc.pa...

Define AccumulatorParam: from pyspark import AccumulatorParam class StringAccumulator(AccumulatorParam): def zero(self, s): return s def addInPlace(self, s1, s2): return s1 + s2 accumulator = sc.accumulator("", StringAccumulator()) def add(x): gl...

Let there be Activity B that can be opened, and can further start more Activities. But, user should not encounter it when navigating back in task activities. The simplest solution is to set the attribute noHistory to true for that <activity> tag in AndroidManifest.xml: <activity a...

Imagine you have the following HTML: <div> <label>Name:</label> John Smith </div> And you need to locate the text "John Smith" after the label element. In this case, you can locate the label element by text and then use .next_sibling property: from ...

BeautifulSoup has a limited support for CSS selectors, but covers most commonly used ones. Use select() method to find multiple elements and select_one() to find a single element. Basic example: from bs4 import BeautifulSoup data = """ <ul> <li class="item&quo...

When the destructor for std::thread is invoked, a call to either join() or detach() must have been made. If a thread has not been joined or detached, then by default std::terminate will be called. Using RAII, this is generally simple enough to accomplish: class thread_joiner { public: thre...

Download a distributed archive from Binaries section of JMeter from Download Apache JMeter page. Depending on the version you downloaded, check minimal Java version requirements and install Java if needed. Ensure the JAVA_HOME environment variable is set and points to a correct version. ...

SyncAdapter /** * Define a sync adapter for the app. * <p/> * <p>This class is instantiated in {@link SyncService}, which also binds SyncAdapter to the system. * SyncAdapter should only be initialized in SyncService, never anywhere else. * <p/> * <p>The system ca...

Sometimes it is appropriate to use an immutable empty collection. The Collections class provides methods to get such collections in an efficient way: List<String> anEmptyList = Collections.emptyList(); Map<Integer, Date> anEmptyMap = Collections.emptyMap(); Set<Number> anEmptySe...

A pure function is a function that, given the same input, will always return the same output and are side-effect free. // This is a pure function function add($a, $b) { return $a + $b; } Some side-effects are changing the filesystem, interacting with databases, printing to the screen. //...

When running from the CLI, PHP exhibits some different behaviours than when run from a web server. These differences should be kept in mind, especially in the case where the same script might be run from both environments. No directory change When running a script from a web server, the current w...

NLog.Extensions.Logging is the official NLog provider for Microsoft's in .NET Core and ASP.NET Core. Here and here are instruction and example respectively.

There are a number of different ways to install the AWS CLI on your machine, depending on what operating system and environment you are using: On Microsoft Windows – use the MSI installer. On Linux, OS X, or Unix – use pip (a package manager for Python software) or install manually with the bundle...

The preferred way of describing dependencies is by using constructor injection which follows Explicit Dependencies Principle: ITestService.cs public interface ITestService { int GenerateRandom(); } TestService.cs public class TestService : ITestService { public int GenerateRando...

Named functions function multiply(a, b) { return a * b; } Anonymous functions let multiply = function(a, b) { return a * b; }; Lambda / arrow functions let multiply = (a, b) => { return a * b; };