Tutorial by Examples: l

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We can optimize a simple xor function for only architectures that support unaligned reads/writes by creating two files that define the function and prefixing them with a build constraint (for an actual example of the xor code which is out of scope here, see crypto/cipher/xor.go in the standard libra...

This is a simple but robust core-data set-up for iOS 10+. There are exactly two way to access core-data: viewContext. The viewContext can only be used from the main thread, and only for reading. strong enqueueCoreDataBlock. All writing should be done using enqueueCoreDataBlock. There is no ne...

// Core Data stack lazy var applicationDocumentsDirectory: NSURL = { let urls = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask) return urls[urls.count-1] }() lazy var managedObjectModel: NSManagedObjectModel = { let modelURL = NSB...

lazy var persistentContainer: NSPersistentContainer = { let container = NSPersistentContainer(name: "ProjectName") container.loadPersistentStores(completionHandler: { (storeDescription, error) in if let error = error { fatalError("Unreso...

Get the Source Package from http://typo3.org/download/ and upload this package to your web server. Put it one level above the document root. For this manual, we will use the .tar.gz file. Use the shell to execute the according commands: /var/www/site/htdocs/$ cd .. /var/www/site/$ wget get.typo3....

go() method The go() method loads a specific URL from the history list. The parameter can either be a number which goes to the URL within the specific position (-1 goes back one page, 1 goes forward one page), or a string. The string must be a partial or full URL, and the function will go to the f...

For Python, Guido van Rossum based the grouping of statements on indentation. The reasons for this are explained in the first section of the "Design and History Python FAQ". Colons, :, are used to declare an indented code block, such as the following example: class ExampleClass: #Eve...

The following example shows a basic main GUI window with a label widget, a toolbar, and a status bar using PyQt4. import sys from PyQt4 import QtGui class App(QtGui.QApplication): def __init__(self, sys_argv): super(App, self).__init__(sys_argv) self.build_ui() ...

This basic code will launch a "Hello world" GUI window using PyQt4: import sys from PyQt4 import QtGui # create instance of QApplication app = QtGui.QApplication(sys.argv) # create QLabel, without parent it will be shown as window label = QtGui.QLabel('Hello world!') label.show(...

The hashlib module allows creating message digest generators via the new method. These generators will turn an arbitrary string into a fixed-length digest: import hashlib h = hashlib.new('sha256') h.update(b'Nobody expects the Spanish Inquisition.') h.digest() # ==> b'.\xdf\xda\xdaVR[\x12\...

hashlib.new requires the name of an algorithm when you call it to produce a generator. To find out what algorithms are available in the current Python interpreter, use hashlib.algorithms_available: import hashlib hashlib.algorithms_available # ==> {'sha256', 'DSA-SHA', 'SHA512', 'SHA224', 'dsa...

An easier approach for some would be to use an existing JavaScript library. This is because it can be tricky to guarantee browser detection is correct, so it can make sense to use a working solution if one is available. One popular browser-detection library is Bowser. Usage example: if (bowser.ms...

When we have two separate array and we want to make key value pair from that two array, we can use array's reduce function like below: var columns = ["Date", "Number", "Size", "Location", "Age"]; var rows = ["2001", "5", "B...

When you are copying a string into a malloced buffer, always remember to add 1 to strlen. char *dest = malloc(strlen(src)); /* WRONG */ char *dest = malloc(strlen(src) + 1); /* RIGHT */ strcpy(dest, src); This is because strlen does not include the trailing \0 in the length. If you take the ...

A programming best practice is to free any memory that has been allocated directly by your own code, or implicitly by calling an internal or external function, such as a library API like strdup(). Failing to free memory can introduce a memory leak, which could accumulate into a substantial amount of...

If realloc fails, it returns NULL. If you assign the value of the original buffer to realloc's return value, and if it returns NULL, then the original buffer (the old pointer) is lost, resulting in a memory leak. The solution is to copy into a temporary pointer, and if that temporary is not NULL, th...

Detailed instructions on getting asp.net-mvc-4 set up or installed.

Before any MPI commands can be run, the environment needs to be initialized, and finalized in the end: int main(int argc, char** argv) { int res; res = MPI_Init(&argc,&argv); if (res != MPI_SUCCESS) { fprintf (stderr, "MPI_Init failed\n"); exit (...

Floating point types (float, double and long double) cannot precisely represent some numbers because they have finite precision and represent the values in a binary format. Just like we have repeating decimals in base 10 for fractions such as 1/3, there are fractions that cannot be represented fini...