Tutorial by Examples: t

Including LaTeX Preample Commands

There are two possible ways of including LaTeX preamble commands (e.g. \usepackage) in a RMarkdown document. 1. Using the YAML option header-includes: --- title: "Including LaTeX Preample Commands in RMarkdown" header-includes: - \renewcommand{\familydefault}{cmss} - \usepacka...

R Language • Creating reports with RMarkdown

A simple authentication POST request with Jsoup

A simple POST request with authentication data is demonstrated below, note that the username and password field will vary depending on the website: final String USER_AGENT = "Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.103 Safari/537.36"; ...

Jsoup • Logging into websites with Jsoup

A more comprehensive authentication POST request with Jsoup

Most websites require a much more complicated process than the one demonstrated above. Common steps for logging into a website are: Get the unique cookie from the initial login form. Inspect the login form to see what the destination url is for the authentication request Parse the login form t...

Jsoup • Logging into websites with Jsoup

Parsing JavaScript Generated Page with Jsoup and HtmUnit

page.html - source code <html> <head> <script src="loadData.js"></script> </head> <body onLoad="loadData()"> <div class="container"> <table id="data" border="1"> <...

Jsoup • Parsing Javascript Generated Pages

Structure of a Simple ASP Page

<%@ Language="VBScript" CodePage = 65001 %> <% Option Explicit Response.Charset = "UTF-8" Response.CodePage = 65001 %> <!doctype html> <html> <head> <title>My First Classic ASP Page</title> </head> <body&gt...

asp-classic • Getting started with asp-classic

Splitting with IFS

To be more clear, let's create a script named showarg: #!/usr/bin/env bash printf "%d args:" $# printf " <%s>" "$@" echo Now let's see the differences: $ var="This is an example" $ showarg $var 4 args: <This> <is> <an> <exa...

Bash • Word splitting

Multiline string literals

VB now allows string literals that split over multiple lines. Old syntax: Dim text As String = "Line1" & Environment.NewLine & "Line2" New syntax: Dim text As String = "Line 1 Line 2"

Visual Basic .NET Language • Visual Basic 14.0 Features

@CompileStatic

Enables a code to be statically compiled. Its bytecode will be closer to Java's, thus having better performance, though some dynamic features won't be available. @groovy.transform.CompileStatic class ListMath { def countSize(List<String> strings) { strings.collect { it.size() }...

groovy • AST Transformations

Using the default Form instance

VB.NET offers default Form instances. The developer does not need to create the instance as it is created behind the scenes. However, it is not preferable to use the default instance all but the simplest programs. Public Class Form1 Public Sub Foo() MessageBox.Show("Bar") ...

Visual Basic .NET Language • Working with Windows Forms

Using uWSGI to run a flask application

The built-in werkzeug server certainly is not suitable for running production servers. The most obvious reason is the fact that the werkzeug server is single-threaded and thus can only handle one request at a time. Because of this we want to use the uWSGI Server to serve our application instead. In...

Flask • Deploying Flask application using uWSGI web server with Nginx

Installing nginx and setting it up for uWSGI

Now we want to install nginx to serve our application. sudo apt-get install nginx # on debian/ubuntu Then we create a configuration for our website cd /etc/nginx/site-available # go to the configuration for available sites # create a file flaskconfig with your favourite editor flaskconfig...

Flask • Deploying Flask application using uWSGI web server with Nginx

Enable streaming from flask

Flask has that feature which lets you stream data from a view by using generators. Let's change the app.py file add from flask import Response add from datetime import datetime add from time import sleep create a new view: @app.route("/time/") def time(): def streamer(): ...

Flask • Deploying Flask application using uWSGI web server with Nginx

CRTP to avoid code duplication

The example in Visitor Pattern provides a compelling use-case for CRTP: struct IShape { virtual ~IShape() = default; virtual void accept(IShapeVisitor&) const = 0; }; struct Circle : IShape { // ... // Each shape has to implement this method the same way ...

C++ • Curiously Recurring Template Pattern (CRTP)

Pitfall: using == to compare strings

A common mistake for Java beginners is to use the == operator to test if two strings are equal. For example: public class Hello { public static void main(String[] args) { if (args.length > 0) { if (args[0] == "hello") { System.out.println(&q...

Java Language • Common Java Pitfalls

Creating zip archive from directory

System.IO.Compression.ZipFile.CreateFromDirectory("myfolder", "archive.zip") Create archive.zip file containing files which are in myfolder. In example paths are relative to program working directory. You can specify absolute paths.

Visual Basic .NET Language • File/Folder Compression

Extracting zip archive to directory

System.IO.Compression.ZipFile.ExtractToDirectory("archive.zip", "myfolder") Extracts archive.zip to myfolder directory. In example paths are relative to program working directory. You can specify absolute paths.

Visual Basic .NET Language • File/Folder Compression

Create zip archive dynamicaly

' Create filestream to file Using fileStream = New IO.FileStream("archive.zip", IO.FileMode.Create) ' open zip archive from stream Using archive = New System.IO.Compression.ZipArchive(fileStream, IO.Compression.ZipArchiveMode.Create) ' create file_in_archive.txt in arch...

Visual Basic .NET Language • File/Folder Compression

Simple self type example

Self types can be used in traits and classes to define constraints on the concrete classes it is mixed to. It is also possible to use a different identifier for the this using this syntax (useful when outer object has to be referenced from an inner object). Assume you want to store some objects. Fo...

Scala Language • Self types

Reads file (/etc/passwd) line by line and field by field

#!/bin/bash FILENAME="/etc/passwd" while IFS=: read -r username password userid groupid comment homedir cmdshell do echo "$username, $userid, $comment $homedir" done < $FILENAME In unix password file, user information is stored line by line, each line consisting of i...

Bash • Read a file (data stream, variable) line-by-line (and/or field-by-field)?

How to compose values and functions using common operators

In Object Oriented Programming a common task is to compose objects (values). In Functional Programming it is as common task to compose values as well as functions. We are used to compose values from our experience of other programming languages using operators like +, -, *, / and so on. Value co...

F# • Operators