Tutorial by Examples: u

Http Request

Html <img id="cats"></img> Dart import 'dart:html'; /// Stores the image in [blob] in the [ImageElement] of the given [selector]. void setImage(selector, blob) { FileReader reader = new FileReader(); reader.onLoad.listen((fe) { ImageElement image = document...

dart • Getting started with dart

Swapping values

Tuples are useful to swap values between 2 (or more) variables without using temporary variables. Example with 2 variables Given 2 variables var a = "Marty McFly" var b = "Emmett Brown" we can easily swap the values (a, b) = (b, a) Result: print(a) // "Emmett Bro...

Swift Language • Tuples

Common Lisp Quick Reference

The Common Lisp Quick Reference is a document which can be printed and bound as a booklet in various layouts to have a printed quick reference for Common Lisp.

common-lisp • ANSI Common Lisp, the language standard and its documentation

Inheritance and methods resolution

To make a class a subclass of another class, use parent pragma: package Point; use strict; ... 1; package Point2D; use strict; use parent qw(Point); ... 1; package Point3D; use strict; use parent qw(Point); ... 1; Perl allows for multiple inheritance: package Point2D; use stri...

Perl Language • Object-oriented Perl

Get previous element

To get the previous element you can use the .prev() method. <ul> <li>Mark</li> <li class="anna">Anna</li> <li>Paul</li> </ul> If you are standing on the "Anna" element and you want to get the previous element, &q...

jQuery • DOM Traversing

On Linux via dpkg

On Debian-based distributions, including Ubuntu, the most straightforward way is to use the .deb installation file. Go to the Scala website. Choose the version you want to install then scroll down and look for scala-x.x.x.deb. You can install the scala deb from command line: sudo dpkg -i scala-x.x...

Scala Language • Setting up Scala

The onBackpressureXXX operators

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(). ...

rx-java • Backpressure

Using a base template

base.twig.html <!DOCTYPE html> <html> <head> <title>{{ title | default('Hello World') }}</title> <link rel="stylesheet" type="text/css" href="theme.css"> {% block css %} {% endblock %} &...

twig • Template inheritance

Change the content of an included template

article.twig.html <article> <h1>{{ article.title }}</h1> {% block content %} <p>{{ article.content }}</p> {% endblock %} </article> articles.twig.html {# use default template for article #} {% for article in articles %} {% include &...

twig • Template inheritance

Collections and Primitive Values

Collections in Java only work for objects. I.e. there is no Map<int, int> in Java. Instead, primitive values need to be boxed into objects, as in Map<Integer, Integer>. Java auto-boxing will enable transparent use of these collections: Map<Integer, Integer> map = new HashMap<&g...

Java Language • Collections

Efficient pixel access using cv::Mat::ptr pointer

If efficiency is important, a fast way to iterate over pixels in a cv::Mat object is to use its ptr<T>(int r) method to obtain a pointer to the beginning of row r (0-based index). According to the matrix type, the pointer will have a different template. For CV_8UC1: uchar* ptr = image.ptr&...

opencv • Pixel Access

Private key is not accepted (OpenSSH clients debug)

By default, most of the information is hidden from the user. You can use -v switches to get a verbose log of the connection attempt, which will usually pinpoint the problem by showing why the behavior is different than you expect. Let's assume you are connecting to the server example.com using ssh ...

Secure Shell • Debugging ssh problems

Skipping some rows from result

ISO/ANSI SQL: SELECT Id, Col1 FROM TableName ORDER BY Id OFFSET 20 ROWS MySQL: SELECT * FROM TableName LIMIT 20, 42424242424242; -- skips 20 for take use very large number that is more than rows in table Oracle: SELECT Id, Col1 FROM (SELECT Id, Col1, row_num...

SQL • SKIP TAKE (Pagination)

Limiting amount of results

ISO/ANSI SQL: SELECT * FROM TableName FETCH FIRST 20 ROWS ONLY; MySQL; PostgreSQL; SQLite: SELECT * FROM TableName LIMIT 20; Oracle: SELECT Id, Col1 FROM (SELECT Id, Col1, row_number() over (order by Id) RowNumber FROM TableName) WHERE RowNumber <= 2...

SQL • SKIP TAKE (Pagination)

Skipping then taking some results (Pagination)

ISO/ANSI SQL: SELECT Id, Col1 FROM TableName ORDER BY Id OFFSET 20 ROWS FETCH NEXT 20 ROWS ONLY; MySQL: SELECT * FROM TableName LIMIT 20, 20; -- offset, limit Oracle; SQL Server: SELECT Id, Col1 FROM (SELECT Id, Col1, row_number() over (order by Id) RowNumbe...

SQL • SKIP TAKE (Pagination)

Pushing and Pulling

Mercurial makes it easy to share your work, and to pull in contributions from other developers. This involves three key steps; cloning, pulling, and pushing. Clone To copy a remote repository to your local disk you "clone" it. To do so simply pass the remote URL you'd like to clone from....

mercurial • Getting started with mercurial

How to configure the build.gradle file

android { ... defaultConfig {...} buildTypes {...} productFlavors { demo { applicationId "com.example.myapp.demo" versionName "1.0-demo" } full { applicationId "com.example.myapp.full"...

android-gradle • Configure Product Flavors

Countries Table

In this example, we have a Countries table. A table for countries has many uses, especially in Financial applications involving currencies and exchange rates. Live example: SQL fiddle Some Market data software applications like Bloomberg and Reuters require you to give their API either a 2 or 3 ch...

SQL • Example Databases and Tables

Add a Customizer Panel

<?php /** * Panel: WPCustomize * * Basic Customizer panel with basic controls. * * @since 1.0.0 * @package WPC */ // Exit if accessed directly. if ( ! defined( 'ABSPATH' ) ) { exit; } // Customize function. if ( ! function_exists( 'wpc_panel_wpcustomize' ) ) { ...

WordPress • Customizer Basics (Add Panel, Section, Setting, Control)

Add a Customizer Section With Basic Settings and their Controls

Panels can have sections, sections can have settings, and settings can have controls. Settings are saved in the database, while the controls for particular settings are only used to display their corresponding setting to the user. This code creates a basic section in the panel from above. Inside a...

WordPress • Customizer Basics (Add Panel, Section, Setting, Control)