Tutorial by Examples: nd

Whitespace is handled by the lexical analyzer before being parsed. The lexical analyzer uses a stack to store indentation levels. At the beginning, the stack contains just the value 0, which is the leftmost position. Whenever a nested block begins, the new indentation level is pushed on the stack, ...

-- Drop an index for column 'name' in table 'my_table' DROP INDEX idx_name ON my_table;

Creating a custom directive with isolated scope will separate the scope inside the directive from the outside scope, in order to prevent our directive from accidentally change the data in the parent scope and restricting it from reading private data from the parent scope. To create an isolated scop...

First, references will be added to the CLR assemblies that will be used. import clr clr.AddReference('System.Windows.Forms') Next the names we will use are imported. from System.Windows.Forms import Application, Form A class will be created for the Hello World form using Form as its subclas...

The two functions fn1 and fn2 can return multiple tensors, but they have to return the exact same number and types of outputs. x = tf.constant(1.) bool = tf.constant(True) def fn1(): return tf.add(x, 1.), x def fn2(): return tf.add(x, 10.), x res1, res2 = tf.cond(bool, fn1, fn2)...

This query selects all books with any rating greater than or equal to four. maybe_good_books = Books.objects.filter(ratings_range__contains=(4, None))

Since npm itself is a Node.js module, it can be updated using itself. If OS is Windows must be running command prompt as Admin npm install -g npm@latest If you want to check for updated versions you can do: npm outdated In order to update a specific package: npm update <package name>...

As seen previously, a closure is nothing but an instance of the Closure class, and different methods can be invoked on them. One of them is bindTo, which, given a closure, will return a new one that is bound to a given object. For example: <?php $myClosure = function() { echo $this->p...

Let's consider this example: <?php $myClosure = function() { echo $this->property; }; class MyClass { public $property; public function __construct($propertyValue) { $this->property = $propertyValue; } } $myInstance = new MyClass('Hello world...

Since PHP7, it is possible to bind a closure just for one call, thanks to the call method. For instance: <?php class MyClass { private $property; public function __construct($propertyValue) { $this->property = $propertyValue; } } $myClosure = function() ...

We define two sets a and b >>> a = {1, 2, 2, 3, 4} >>> b = {3, 3, 4, 4, 5} NOTE: {1} creates a set of one element, but {} creates an empty dict. The correct way to create an empty set is set(). Intersection a.intersection(b) returns a new set with elements present in bot...

Running git reset --hard moves refs to the specified hash/ref. Moving MyBranch to b8dc53: $ git checkout MyBranch # moves HEAD to MyBranch $ git reset --hard b8dc53 # makes MyBranch point to b8dc53

Common Lisp already has a reverse function, but if it didn't, then it could be implemented easily using reduce. Given a list like (1 2 3) === (cons 1 (cons 2 (cons 3 '()))) the reversed list is (cons 3 (cons 2 (cons 1 '()))) === (3 2 1) That may not be an obvious use of reduce, but if we ha...

The intrinsic pack function packs an array into a vector, selecting elements based on a given mask. The function has two forms PACK(array, mask) PACK(array, mask, vector) (that is, the vector argument is optional). In both cases array is an array, and mask of logical type and conformable with...

This feeds a while loop with the output of a grep command: while IFS=":" read -r user _ do # "$user" holds the username in /etc/passwd done < <(grep "hello" /etc/passwd)

Python 3 allows you to define function arguments which can only be assigned by keyword, even without default values. This is done by using star * to consume additional positional parameters without setting the keyword parameters. All arguments after the * are keyword-only (i.e. non-positional) arg...

Sometimes a column should show different content than just the toString value of the cell item. In this case the TableCells created by the cellFactory of the TableColumn is customized to change the layout based on the item. Important Note: TableView only creates the TableCells that are shown in the...

Ubuntu On recent Ubuntu versions, you can install an up-to-date version of CouchDB with sudo apt-get install couchdb. For older versions, such as Ubuntu 14.04, you should run: sudo add-apt-repository ppa:couchdb/stable -y sudo apt-get update sudo apt-get install couchdb -y Fedora To install ...

Hashes can be freely converted to and from arrays. Converting a hash of key/value pairs into an array will produce an array containing nested arrays for pair: { :a => 1, :b => 2 }.to_a # => [[:a, 1], [:b, 2]] In the opposite direction a Hash can be created from an array of the same form...

Basics Anonymous functions are a powerful tool of the MATLAB language. They are functions that exist locally, that is: in the current workspace. However, they do not exist on the MATLAB path like a regular function would, e.g. in an m-file. That is why they are called anonymous, although they can h...