Tutorial by Examples: b

Lets say we have a class as (defclass person () (name email age)) To obtain the names of the slots of the class we use the function class-slots. This can be found in the closer-mop package, provided by the closer-mop system. To load it the running lisp image we use (ql:quickload :closer-mop)....

CREATE DATABASE stackoverflow; USE stackoverflow; Create table stack( id_user int NOT NULL, username varchar(30) NOT NULL, password varchar(30) NOT NULL ); ALTER TABLE stack ADD COLUMN submit date NOT NULL; -- add new column ALTER TABLE stack DROP COLUMN submit; -- drop col...

itertools.combinations will return a generator of the k-combination sequence of a list. In other words: It will return a generator of tuples of all the possible k-wise combinations of the input list. For Example: If you have a list: a = [1,2,3,4,5] b = list(itertools.combinations(a, 2)) print ...

import java.io.*; import java.net.Socket; public class Main { public static void main(String[] args) throws IOException {//We don't handle Exceptions in this example //Open a socket to stackoverflow.com, port 80 Socket socket = new Socket("stackoverflow.com",8...

ob_start is especially handy when you have redirections on your page. For example, the following code won't work: Hello! <?php header("Location: somepage.php"); ?> The error that will be given is something like: headers already sent by <xxx> on line <xxx>. In or...

This book is known as CLtL2. This is the second edition of the book Common Lisp the Language. It was published in 1990, before the ANSI CL standard was final. It took the original language definition from the first edition (published in 1984) and described all changes in the standardization process...

data.table extends reshape2's melt & dcast functions (Reference: Efficient reshaping using data.tables) library(data.table) ## generate some data dt <- data.table( name = rep(c("firstName", "secondName"), each=4), numbers = rep(1:4, 2), value = rnorm(8) ) ...

When PyInstaller is used without any options to bundle myscript.py , the default output is a single folder (named myscript) containing an executable named myscript (myscript.exe in windows) along with all the necessary dependencies. The app can be distributed by compressing the folder into a zip fi...

pyinstaller myscript.py -F The options to generate a single file are -F or --onefile. This bundles the program into a single myscript.exe file. Single file executable are slower than the one-folder bundle. They are also harder to debug.

In HTTP 1.1, a minimal HTTP request consists of a request line and a Host header: GET /search HTTP/1.1 \r\n Host: google.com \r\n \r\n The first line has this format: Method Request-URI HTTP-Version CRLF Method should be a valid HTTP method; one of [1][2]: OPTIONS GET HEAD POST PUT ...

Some HTTP requests may contain a message body. This is additional data that the server will use to process the request. Message bodies are most often used in POST or PATCH and PUT requests, to provide new data that the server should apply to a resource. Requests that include a message body should a...

The split-sequence library provides a function split-sequence, which allows to split on elements of a sequence (split-sequence:split-sequence #\Space "John Doe II") ;; => ("John" "Doe" "II")

From the official documentation: If you want to get advanced, you can also open up the project file for a specific platform by opening the required XCode or Android Eclipse project in platforms/PLATFORM inside the root of your project. Then, you can build and test from inside the platform-specifi...

There are several good examples of using lambdas as a FunctionalInterface in simple scenarios. A fairly common use case that can be improved by lambdas is what is called the Execute-Around pattern. In this pattern, you have a set of standard setup/teardown code that is needed for multiple scenarios ...

This example uses a push button (tact switch) attached to digital pin 2 and GND, using an internal pull-up resistor so pin 2 is HIGH when the button is not pressed. const int LED_PIN = 13; const int INTERRUPT_PIN = 2; volatile bool ledState = LOW; void setup() { pinMode(LED_PIN, OUTPUT); ...

Generic parameters can also be bound to more than one type using the T extends Type1 & Type2 & ... syntax. Let's say you want to create a class whose Generic type should implement both Flushable and Closeable, you can write class ExampleClass<T extends Flushable & Closeable> { }...

A JSON Object is surrounded by curly braces and contains key-value pairs. { "key1": "value1", "key2": "value2", ... } Keys must be valid strings, thus surrounded by double quotation marks. Values can be JSON objects, numbers, strings, arrays, or one of the...

Unlike many other languages, Perl does not have constructors that allocate memory for your objects. Instead, one should write a class method that both create a data structure and populate it with data (you may know it as the Factory Method design pattern). package Point; use strict; sub new { ...

In Perl, the difference between class (static) and object (instance) methods is not so strong as in some other languages, but it still exists. The left operand of the arrow operator -> becomes the first argument of the method to be called. It may be either a string: # the first argument of new ...

Most developers encounter backpressure when their application fails with MissingBackpressureException and the exception usually points to the observeOn operator. The actual cause is usually the non-backpressured use of PublishSubject, timer() or interval() or custom operators created via create(). ...