Tutorial by Examples: en

Lens operators have useful variants that operate in stateful contexts. They are obtained by replacing ~ with = in the operator name. (+~) :: Num a => ASetter s t a a -> a -> s -> t (+=) :: (MonadState s m, Num a) => ASetter' s a -> a -> m () Note: The stateful variants ar...

For the sample XML (without namespaces): This XPath, /r/e will select this element: <e a="1"/>

Python 2.x2.3 Objects of different types can be compared. The results are arbitrary, but consistent. They are ordered such that None is less than anything else, numeric types are smaller than non-numeric types, and everything else is ordered lexicographically by type. Thus, an int is less than a st...

Enums can define abstract methods, which each enum member is required to implement. enum Action { DODGE { public boolean execute(Player player) { return player.isAttacking(); } }, ATTACK { public boolean execute(Player player) { re...

Enums have been backported from Python 3.4 to Python 2.4 through Python 3.3. You can get this the enum34 backport from PyPI. pip install enum34 Creation of an enum is identical to how it works in Python 3.4+ from enum import Enum class Color(Enum): red = 1 green = 2 blue = 3 ...

${#array[@]} gives the length of the array ${array[@]}: array=('first element' 'second element' 'third element') echo "${#array[@]}" # gives out a length of 3 This works also with Strings in single elements: echo "${#array[0]}" # gives out the lenght of the string at ele...

As shown in Declaring Namespaces, we can define a class in a namespace as follows: namespace MyProject\Shapes; class Rectangle { ... } To reference this class the full path (including the namespace) needs to be used: $rectangle = new MyProject\Shapes\Rectangle(); This can be shortened by ...

When defining discriminated unions you can name elements of tuple types and use these names during pattern matching. type Shape = | Circle of diameter:int | Rectangle of width:int * height:int let shapeIsTenWide = function | Circle(diameter=10) | Rectangle(width=10) -> t...

Clicking the Select an element in the page to inspect it button in the upper left corner of the Elements tab in Chrome or Inspector tab in Firefox, available from Developer Tools, and then clicking on a element of the page highlights the element and assigns it to the $0 variable. Elements inspecto...

package main import ( "fmt" "io/ioutil" ) func main() { files, err := ioutil.ReadDir(".") if err != nil { panic(err) } fmt.Println("Files and folders in the current directory:") for _, fileInfo := range fi...

Taking a complex JSON document in a table: CREATE TABLE mytable (data JSONB NOT NULL); CREATE INDEX mytable_idx ON mytable USING gin (data jsonb_path_ops); INSERT INTO mytable VALUES($$ { "name": "Alice", "emails": [ "[email protected]", ...

Strings in JavaScript can be enclosed in Single quotes 'hello', Double quotes "Hello" and (from ES2015, ES6) in Template Literals (backticks) `hello`. var hello = "Hello"; var world = 'world'; var helloW = `Hello World`; // ES2015 / ES6 Strings can be created...

You can require a generic type to extend multiple upper bounds. Example: we want to sort a list of numbers but Number doesn't implement Comparable. public <T extends Number & Comparable<T>> void sortNumbers( List<T> n ) { Collections.sort( n ); } In this example T must...

Swift textView.textAlignment = .left Objective-C textView.textAlignment = NSTextAlignmentLeft;

Auto-implemented properties were introduced in C# 3. An auto-implemented property is declared with an empty getter and setter (accessors): public bool IsValid { get; set; } When an auto-implemented property is written in your code, the compiler creates a private anonymous field that can only be...

The following code snippet shows how to open the Google Play Store Listing of your app in a safe way. Usually you want to use it when asking the user to leave a review for your app. private void openPlayStore() { String packageName = getPackageName(); Intent playStoreIntent = new Intent(I...

This is the primary purpose of cat. cat file1 file2 file3 > file_all cat can also be used similarly to concatenate files as part of a pipeline, e.g. cat file1 file2 file3 | grep foo

An alternative community de facto standard is an addon called ember-concurrency that makes a lot of the promise confusion go away. It can be installed with the command ember install ember-concurrency. Pros Intuitive reasoning of complex asynchronous code. Offers a complete API for managing tas...

Units of measure are additional type annotations that can be added to floats or integers. They can be used to verify at compile time that calculations are using units consistently. To define annotations: [<Measure>] type m // meters [<Measure>] type s // seconds [<Measure>] typ...

If you need to remove one or more elements from a slice, or if you need to work with a sub slice of another existing one; you can use the following method. Following examples uses slice of int, but that works with all type of slice. So for that, we need a slice, from witch we will remove some ...