Tutorial by Examples: l

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...

When the following is compiled, it will return a different value depending on which directives are defined. // Compile with /d:A or /d:B to see the difference string SomeFunction() { #if A return "A"; #elif B return "B"; #else return "C"; #endif ...

Compiler warnings can be generated using the #warning directive, and errors can likewise be generated using the #error directive. #if SOME_SYMBOL #error This is a compiler Error. #elif SOME_OTHER_SYMBOL #warning This is a compiler Warning. #endif

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...

Use #region and #endregion to define a collapsible code region. #region Event Handlers public void Button_Click(object s, EventArgs e) { // ... } public void DropDown_SelectedIndexChanged(object s, EventArgs e) { // ... } #endregion These directives are only beneficial whe...

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...

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...

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...

// Create an array with a fixed size and type. var array = new Uint8Array(5); // Generate cryptographically random values crypto.getRandomValues(array); // Print the array to the console console.log(array); crypto.getRandomValues(array) can be used with instances of the following classes...

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...

6 var myIterableObject = {}; // An Iterable object must define a method located at the Symbol.iterator key: myIterableObject[Symbol.iterator] = function () { // The iterator should return an Iterator object return { // The Iterator object must implement a method, next() next: func...

dynamic foo = 123; Console.WriteLine(foo + 234); // 357 Console.WriteLine(foo.ToUpper()) // RuntimeBinderException, since int doesn't have a ToUpper method foo = "123"; Console.WriteLine(foo + 234); // 123234 Console.WriteLine(foo.ToUpper()): // NOW A STRING

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...

A prvalue (pure-rvalue) expression is an expression which lacks identity, whose evaluation is typically used to initialize an object, and which can be implicitly moved from. These include, but are not limited to: Expressions that represent temporary objects, such as std::string("123"). ...

An xvalue (eXpiring value) expression is an expression which has identity and represents an object which can be implicitly moved from. The general idea with xvalue expressions is that the object they represent is going to be destroyed soon (hence the "eXpiring" part), and therefore implici...

An lvalue expression is an expression which has identity, but cannot be implicitly moved from. Among these are expressions that consist of a variable name, function name, expressions that are built-in dereference operator uses and expressions that refer to lvalue references. The typical lvalue is s...

A glvalue (a "generalized lvalue") expression is any expression which has identity, regardless of whether it can be moved from or not. This category includes lvalues (expressions that have identity but can't be moved from) and xvalues (expressions that have identity, and can be moved from)...

An rvalue expression is any expression which can be implicitly moved from, regardless of whether it has identity. More precisely, rvalue expressions may be used as the argument to a function that takes a parameter of type T && (where T is the type of expr). Only rvalue expressions may be gi...