Tutorial by Examples: u

You can combine object initializers with constructors to initialize types if necessary. Take for example a class defined as such: public class Book { public string Title { get; set; } public string Author { get; set; } public Book(int id) { //do things } // the...

length counts the occurences of elements a in a foldable structure t a. ghci> length [7, 2, 9] -- t ~ [] 3 ghci> length (Right 'a') -- t ~ Either e 1 -- 'Either e a' may contain zero or one 'a' ghci> length (Left "foo") -- t ~ Either String 0 ghci> length (3, True) ...

Any fold can be run in the opposite direction with the help of the Dual monoid, which flips an existing monoid so that aggregation goes backwards. newtype Dual a = Dual { getDual :: a } instance Monoid m => Monoid (Dual m) where mempty = Dual mempty (Dual x) `mappend` (Dual y) = Dua...

import Data.Traversable as Traversable data MyType a = -- ... instance Traversable MyType where traverse = -- ... Every Traversable structure can be made a Foldable Functor using the fmapDefault and foldMapDefault functions found in Data.Traversable. instance Functor MyType where ...

A traversal can be run in the opposite direction with the help of the Backwards applicative functor, which flips an existing applicative so that composed effects take place in reversed order. newtype Backwards f a = Backwards { forwards :: f a } instance Applicative f => Applicative (Backward...

The standard (section 23.3.7) specifies that a specialization of vector<bool> is provided, which optimizes space by packing the bool values, so that each takes up only one bit. Since bits aren't addressable in C++, this means that several requirements on vector are not placed on vector<bool...

A compiler symbol is a keyword that is defined at compile-time that can be checked for to conditionally execute specific sections of code. There are three ways to define a compiler symbol. They can be defined via code: #define MYSYMBOL They can be defined in Visual Studio, under Project Propert...

Line #line controls the line number and filename reported by the compiler when outputting warnings and errors. void Test() { #line 42 "Answer" #line filename "SomeFile.cs" int life; // compiler warning CS0168 in "SomeFile.cs" at Line 42 #line defa...

Sometimes you may have a form and want to submit it using ajax. Suppose you have this simple form - <form id="ajax_form" action="form_action.php"> <label for="name">Name :</label> <input name="name" id="name" type="t...

package main import ( "log" "net/http" ) func main() { // Create a mux for routing incoming requests m := http.NewServeMux() // All URLs will be handled by this function m.HandleFunc("/", func(w http.ResponseWriter, r *http.Reque...

#import <Foundation/Foundation.h> @interface Car:NSObject { NSString *CarMotorCode; NSString *CarChassisCode; } - (instancetype)initWithMotorValue:(NSString *) motorCode andChassisValue:(NSInteger)chassisCode; - (void) startCar; - (void) stopCar; @end @implementation Car...

C11 Reading an object will cause undefined behavior, if the object is1: uninitialized defined with automatic storage duration it's address is never taken The variable a in the below example satisfies all those conditions: void Function( void ) { int a; int b = a; } 1 (Quo...

The following will retrieve a channel object for the twitch channel. If the request was successful the channel object will be logged to the console. $.ajax({ type: 'GET', url: 'https://api.twitch.tv/kraken/channels/twitch', headers: { 'Client-ID': '...' }, success: function(data...

Array types inherit their equals() (and hashCode()) implementations from java.lang.Object, so equals() will only return true when comparing against the exact same array object. To compare arrays for equality based on their values, use java.util.Arrays.equals, which is overloaded for all array types...

With constructor: Vector v1 = new Vector(); v1.X = 1; v1.Y = 2; v1.Z = 3; Console.WriteLine("X = {0}, Y = {1}, Z = {2}",v1.X,v1.Y,v1.Z); // Output X=1,Y=2,Z=3 Vector v1 = new Vector(); //v1.X is not assigned v1.Y = 2; v1.Z = 3; Console.WriteLine("X = {0}, Y = {1}, Z =...

Setting values Using Unicode directly var str: String = "I want to visit 北京, Москва, मुंबई, القاهرة, and 서울시. 😊" var character: Character = "🌍" Using hexadecimal values var str: String = "\u{61}\u{5927}\u{1F34E}\u{3C0}" // a大🍎π var character: Character = &quo...

Swift's C interoperability allows you to use functions and types from the C standard library. On Linux, the C standard library is exposed via the Glibc module; on Apple platforms it's called Darwin. #if os(macOS) || os(iOS) || os(tvOS) || os(watchOS) import Darwin #elseif os(Linux) import Glibc...

using System; public static void Main() { var value = GetValue(); Console.WriteLine(value); // dynamics are useful! } private static dynamic GetValue() { return "dynamics are useful!"; }

You can use a colon and the standard numeric format syntax to control how numbers are formatted. var decimalValue = 120.5; var asCurrency = $"It costs {decimalValue:C}"; // String value is "It costs $120.50" (depending on your local currency settings) var withThreeDecimal...

Expressions in C++ are assigned a particular value category, based on the result of those expressions. Value categories for expressions can affect C++ function overload resolution. Value categories determines two important-but-separate properties about an expression. One property is whether the exp...