Tutorial by Examples: le

Simple Switch with Default Condition

The Default keyword is used to execute an action when no other conditions match the input value. Example: switch('Condition') { 'Skip Condition' { 'First Action' } 'Skip This Condition Too' { 'Second Action' } Default { 'Default Action' } } Output: D...

PowerShell • Switch statement

Closing a serial port even if lost, deleted or overwritten

Assuming you created the serial port object s as in this example, then to close it fclose(s) However, sometimes you can accidentally lose the port (e.g. clear, overwrite, change scope, etc...), and fclose(s) will no longer work. The solution is easy fclose(instrfindall) More info at instrfin...

MATLAB Language • Using serial ports

Selecting specified number of records

The SQL 2008 standard defines the FETCH FIRST clause to limit the number of records returned. SELECT Id, ProductName, UnitPrice, Package FROM Product ORDER BY UnitPrice DESC FETCH FIRST 10 ROWS ONLY This standard is only supported in recent versions of some RDMSs. Vendor-specific non-stand...

SQL • SELECT

Comprehensions involving tuples

The for clause of a list comprehension can specify more than one variable: [x + y for x, y in [(1, 2), (3, 4), (5, 6)]] # Out: [3, 7, 11] [x + y for x, y in zip([1, 3, 5], [2, 4, 6])] # Out: [3, 7, 11] This is just like regular for loops: for x, y in [(1,2), (3,4), (5,6)]: print(x+y) ...

Python Language • List comprehensions

Lexicographical comparison

Two std::strings can be compared lexicographically using the operators ==, !=, <, <=, >, and >=: std::string str1 = "Foo"; std::string str2 = "Bar"; assert(!(str1 < str2)); assert(str > str2); assert(!(str1 <= str2)); assert(str1 >= str2); assert...

C++ • std::string

Embedding external SVG files in HTML

You can use the <img> or <object> elements to embed external SVG elements. Setting the height and width is optional but is highly recommended. Using the image element <img src="attention.svg" width="50" height="50"> Using <img> does not allo...

HTML • SVG

Variable Names

Variables hold data. Name them after what they're used for, not after their data type or scope, using a noun. If you feel compelled to number your variables (e.g. thing1, thing2, thing3), then consider using an appropriate data structure instead (e.g. an array, a Collection, or a Dictionary). Names...

VBA • Naming Conventions

Repeat-while loop

Similar to the while loop, only the control statement is evaluated after the loop. Therefore, the loop will always execute at least once. var i: Int = 0 repeat { print(i) i += 1 } while i < 3 // 0 // 1 // 2

Swift Language • Loops

while loop

A while loop will execute as long as the condition is true. var count = 1 while count < 10 { print("This is the \(count) run of the loop") count += 1 }

Swift Language • Loops

Matching multiple patterns

It's possible to treat multiple, distinct values the same way, using |: enum Colour { Red, Green, Blue, Cyan, Magenta, Yellow, Black } enum ColourModel { RGB, CMYK } // let's take an example colour let colour = Colour::Red; let model = match ...

Rust • Pattern Matching

Select children of element

To select the children of an element you can use the children() method. <div class="parent"> <h2>A headline</h2> <p>Lorem ipsum dolor sit amet...</p> <p>Praesent quis dolor turpis...</p> </div> Change the color of all the ...

jQuery • DOM Traversing

Simple Bar Chart

index.html <!doctype html> <html> <head> <title>D3 Sample</title> </head> <body>  <div id=...

d3.js • Getting started with d3.js

Statically Initialized Singleton

public class Singleton { private readonly static Singleton instance = new Singleton(); private Singleton() { } public static Singleton Instance => instance; } This implementation is thread-safe because in this case instance object is initialized in the static constructor. The ...

C# Language • Singleton Implementation

Lazy, thread-safe Singleton (using Double Checked Locking)

This thread-safe version of a singleton was necessary in the early versions of .NET where static initialization was not guaranteed to be thread-safe. In more modern versions of the framework a statically initialized singleton is usually preferred because it is very easy to make implementation mistak...

C# Language • Singleton Implementation

Underlying references of named method delegates

When assigning named methods to delegates, they will refer to the same underlying object if: They are the same instance method, on the same instance of a class They are the same static method on a class public class Greeter { public void WriteInstance() { Console.Write...

C# Language • Delegates

Declaring a delegate type

The following syntax creates a delegate type with name NumberInOutDelegate, representing a method which takes an int and returns an int. public delegate int NumberInOutDelegate(int input); This can be used as follows: public static class Program { static void Main() { Number...

C# Language • Delegates

The Func, Action and Predicate delegate types

The System namespace contains Func<..., TResult> delegate types with between 0 and 15 generic parameters, returning type TResult. private void UseFunc(Func<string> func) { string output = func(); // Func with a single generic type parameter returns that type Console.WriteLine...

C# Language • Delegates

Assigning a named method to a delegate

Named methods can be assigned to delegates with matching signatures: public static class Example { public static int AddOne(int input) { return input + 1; } } Func<int,int> addOne = Example.AddOne Example.AddOne takes an int and returns an int, its signature ...

C# Language • Delegates

Delegate Equality

Calling .Equals() on a delegate compares by reference equality: Action action1 = () => Console.WriteLine("Hello delegates"); Action action2 = () => Console.WriteLine("Hello delegates"); Action action1Again = action1; Console.WriteLine(action1.Equals(action1)) // True ...

C# Language • Delegates

Assigning to a delegate by lambda

Lambdas can be used to create anonymous methods to assign to a delegate: Func<int,int> addOne = x => x+1; Note that the explicit declaration of type is required when creating a variable this way: var addOne = x => x+1; // Does not work

C# Language • Delegates