Tutorial by Examples: e

process.argv is an array containing the command line arguments. The first element will be node, the second element will be the name of the JavaScript file. The next elements will be any additional command line arguments. Code Example: Output sum of all command line arguments index.js var sum = 0...

Here we make a simple echo websocket using asyncio. We define coroutines for connecting to a server and sending/receiving messages. The communcations of the websocket are run in a main coroutine, which is run by an event loop. This example is modified from a prior post. import asyncio import ai...

Install cx_Freeze from here Unzip the folder and run these commands from that directory: python setup.py build sudo python setup.py install Create a new directory for your python script and create a "setup.py" file in the same directory with the following content: application_title ...

A singleton is a pattern that restricts the instantiation of a class to one instance/object. Using a decorator, we can define a class as a singleton by forcing the class to either return an existing instance of the class or create a new instance (if it doesn't exist). def singleton(cls): i...

Using vanilla mathematics: var from:Point = new Point(100, 50); var to:Point = new Point(80, 95); var angle:Number = Math.atan2(to.y - from.y, to.x - from.x); Using a new vector representing the difference between the first two: var difference:Point = to.subtract(from); var angle:Number ...

Using vanilla mathematics: var from:Point = new Point(300, 10); var to:Point = new Point(75, 40); var a:Number = to.x - from.x; var b:Number = to.y - from.y; var distance:Number = Math.sqrt(a * a + b * b); Using inbuilt functionality of Point: var distance:Number = to.subtract(from).len...

var degrees:Number = radians * 180 / Math.PI;

var radians:Number = degrees / 180 * Math.PI;

A whole circle is 360 degrees or Math.PI * 2 radians. Half of those values follows to be 180 degrees or Math.PI radians. A quarter is then 90 degrees or Math.PI / 2 radians. To get a segment as a percentage of a whole circle in radians: function getSegment(percent:Number):Number { retur...

Assuming you have the angle you'd like to move in and an object with x and y values you want to move: var position:Point = new Point(10, 10); var angle:Number = 1.25; You can move along the x axis with Math.cos: position.x += Math.cos(angle); And the y axis with Math.sin: position.y += Mat...

You can test whether a point is inside a rectangle using Rectangle.containsPoint(): var point:Point = new Point(5, 5); var rectangle:Rectangle = new Rectangle(0, 0, 10, 10); var contains:Boolean = rectangle.containsPoint(point); // true

A string can reversed using the built-in reversed() function, which takes a string and returns an iterator in reverse order. >>> reversed('hello') <reversed object at 0x0000000000000000> >>> [char for char in reversed('hello')] ['o', 'l', 'l', 'e', 'h'] reversed() can ...

In addition to predicates functioning as specs, you can register a spec globally using clojure.spec/def. def requires that a spec being registered is named by a namespace-qualified keyword: (clojure.spec/def ::odd-nums odd?) ;;=> :user/odd-nums (clojure.spec/valid? ::odd-nums 1) ;;=> tru...

clojure.spec/and & clojure.spec/or can be used to create more complex specs, using multiple specs or predicates: (clojure.spec/def ::pos-odd (clojure.spec/and odd? pos?)) (clojure.spec/valid? ::pos-odd 1) ;;=> true (clojure.spec/valid? ::pos-odd -3) ;;=> false or works similarl...

You can spec a record as follows: (clojure.spec/def ::name string?) (clojure.spec/def ::age pos-int?) (clojure.spec/def ::occupation string?) (defrecord Person [name age occupation]) (clojure.spec/def ::person (clojure.spec/keys :req-un [::name ::age ::occupation])) (clojure.spec/valid? ...

You can spec a map by specifying which keys should be present in the map: (clojure.spec/def ::name string?) (clojure.spec/def ::age pos-int?) (clojure.spec/def ::occupation string?) (clojure.spec/def ::person (clojure.spec/keys :req [::name ::age ::occupation])) (clojure.spec/valid? ::perso...

You can spec collections in a number of ways. coll-of allows you to spec collections and provide some additional constraints. Here's a simple example: (clojure.spec/valid? (clojure.spec/coll-of int?) [1 2 3]) ;; => true (clojure.spec/valid? (clojure.spec/coll-of int?) '(1 2 3)) ;; => tru...

spec can describe and be used with arbitrary sequences. It supports this via a number of regex spec operations. (clojure.spec/valid? (clojure.spec/cat :text string? :int int?) ["test" 1]) ;;=> true cat requires labels for each spec used to describe the sequence. cat describes a seq...

Sometimes you may only need to simulate an event with two outcomes, maybe with different probabilities, but you may find yourself in a situation that calls for many possible outcomes with different probabilities. Let's imagine you want to simulate an event that has six equally probable outcomes. T...

Consider a production table called questions_mysql and a table iwtQuestions (imported worktable) representing the last batch of imported CSV data from a LOAD DATA INFILE. The worktable is truncated before the import, the data is imported, and that process is not shown here. Update our production da...