Tutorial by Examples: f

This is an example of dereferencing a NULL pointer, causing undefined behavior. int * pointer = NULL; int value = *pointer; /* Dereferencing happens here */ A NULL pointer is guaranteed by the C standard to compare unequal to any pointer to a valid object, and dereferencing it invokes undefined...

int i = 42; i = i++; /* Assignment changes variable, post-increment as well */ int a = i++ + i--; Code like this often leads to speculations about the "resulting value" of i. Rather than specifying an outcome, however, the C standards specify that evaluating such an expression produc...

int foo(void) { /* do stuff */ /* no return here */ } int main(void) { /* Trying to use the (not) returned value causes UB */ int value = foo(); return 0; } When a function is declared to return a value then it has to do so on every possible code path through it. Undefined beh...

The ls command lists the contents of a specified directory, excluding dotfiles. If no directory is specified then, by default, the contents of the current directory are listed. Listed files are sorted alphabetically, by default, and aligned in columns if they don’t fit on one line. $ ls apt conf...

The type of the literal Prelude> :t 1.0 1.0 :: Fractional a => a Choosing a concrete type with annotations You can specify the type with a type annotation. The only requirement is that the type must have a Fractional instance. Prelude> 1.0 :: Double 1.0 it :: Double Prelude> 1....

println! (and its sibling, print!) provides a convenient mechanism for producing and printing text that contains dynamic data, similar to the printf family of functions found in many other languages. Its first argument is a format string, which dictates how the other arguments should be printed as t...

Struct fields whose names begin with an uppercase letter are exported. All other names are unexported. type Account struct { UserID int // exported accessToken string // unexported } Unexported fields can only be accessed by code within the same package. As such, if you are ev...

The filter() method accepts a test function, and returns a new array containing only the elements of the original array that pass the test provided. // Suppose we want to get all odd number in an array: var numbers = [5, 32, 43, 4]; 5.1 var odd = numbers.filter(function(n) { return n % 2 !=...

PorterDuff.Mode is used to create a PorterDuffColorFilter. A color filter modifies the color of each pixel of a visual resource. ColorFilter filter = new PorterDuffColorFilter(Color.BLUE, PorterDuff.Mode.SRC_IN); The above filter will tint the non-transparent pixels to blue color. The color fil...

An Xfermode (think "transfer" mode) works as a transfer step in drawing pipeline. When an Xfermode is applied to a Paint, the pixels drawn with the paint are combined with underlying pixels (already drawn) as per the mode: paint.setColor(Color.BLUE); paint.setXfermode(new PorterDuffXferm...

In info.plist set View controller-based status bar appearance to YES In view controllers not contained by UINavigationController implement this method. In Objective-C: - (UIStatusBarStyle)preferredStatusBarStyle { return UIStatusBarStyleLightContent; } In Swift: override func pre...

A simple literal function, printing Hello! to stdout: package main import "fmt" func main() { func(){ fmt.Println("Hello!") }() } play it on playground A literal function, printing the str argument to stdout: package main import "fmt&quot...

A variadic function can be called with any number of trailing arguments. Those elements are stored in a slice. package main import "fmt" func variadic(strs ...string) { // strs is a slice of string for i, str := range strs { fmt.Printf("%d: %s\n", i, ...

Warning: be sure you have at least 15 GB of free disk space. Compilation in Ubuntu >=13.04 Option A) Use Git Use git if you want to stay in sync with the latest Ubuntu kernel source. Detailed instructions can be found in the Kernel Git Guide. The git repository does not include necessary ...

In order to test the beginning and ending of a given string in Python, one can use the methods str.startswith() and str.endswith(). str.startswith(prefix[, start[, end]]) As it's name implies, str.startswith is used to test whether a given string starts with the given characters in prefix. >...

Strict mode can be applied on entire scripts by placing the statement "use strict"; before any other statements. "use strict"; // strict mode now applies for the rest of the script Strict mode is only enabled in scripts where you define "use strict". You can combin...

Strict mode can also be applied to single functions by prepending the "use strict"; statement at the beginning of the function declaration. function strict() { "use strict"; // strict mode now applies to the rest of this function var innerFunction = function () { ...

NaN ("Not a Number") is a special value defined by the IEEE Standard for Floating-Point Arithmetic, which is used when a non-numeric value is provided but a number is expected (1 * "two"), or when a calculation doesn't have a valid number result (Math.sqrt(-1)). Any equality or ...

Python's str type also features a number of methods that can be used to evaluate the contents of a string. These are str.isalpha, str.isdigit, str.isalnum, str.isspace. Capitalization can be tested with str.isupper, str.islower and str.istitle. str.isalpha str.isalpha takes no arguments and retu...

try { StyledDocument doc = new DefaultStyledDocument(); doc.insertString(0, "This is the beginning text", null); doc.insertString(doc.getLength(), "\nInserting new line at end of doc", null); MutableAttributeSet attrs = new SimpleAttributeSet(); StyleCons...