Tutorial by Examples: el

Suppose we want to read and stack a bunch of similarly-formatted files. The quick solution is: rbindlist(lapply(list.files(patt="csv$"), fread), id=TRUE) We might not be satisfied with this for a couple reasons: It might run into errors when reading with fread or when stacking with ...

Install node modules npm install express npm install socket.io Node.js server const express = require('express'); const app = express(); const server = app.listen(3000,console.log("Socket.io Hello Wolrd server started!")); const io = require('socket.io')(server); io.on('connec...

[TestFixture] public class UnitTest1 { class Message { public string Text { get; } = "Hello World"; } [Test] public void HelloWorldTest() { // Act var message = new Message(); // Assert Assert.That(message.Tex...

array = [1, 2, 3, 4] [first] = array # 1 [..., last] = array # 4 [first, middle..., last] = array # first is 1, middle is [2, 3], last is 4

The unset command is used to remove one or more variables. unset ?-nocomplain? ?--? ?name name name name? Each name is a variable name specified in any of the ways acceptable to the set command. If a name refers to an element of an array then that element is removed without affecting the rema...

When object's are linked by a lookup or master-detail relationship, the parent records field's can be referenced from the child record or 'base object' in a query. This is also known as upwards traversal. SELECT FirstName, Account.Name, Account.Category__c FROM Contact It's possible to traverse ...

The CharField is used for storing defined lengths of text. In the example below up to 128 characters of text can be stored in the field. Entering a string longer than this will result in a validation error being raised. from django.db import models class MyModel(models.Model): name = models...

Create a new project.json and example Program.cs: dotnet new Restore needed packages: dotnet restore Compile and run the example: dotnet run

Given these two CSV files: $ cat file1 1,line1 2,line2 3,line3 4,line4 $ cat file2 1,line3 2,line4 3,line5 4,line6 To print those lines in file2 whose second column occurs also in the first file we can say: $ awk -F, 'FNR==NR {lines[$2]; next} $2 in lines' file1 file2 1,line3 2,line4...

Gradle will only run one task at a time by default, regardless of the project structure. By using the --parallel switch, you can force Gradle to execute independent subprojects - those that have no implicit or explicit project dependencies between one another - in parallel, allowing it to run multip...

The Gradle team works regularly on improving the performance of different aspects of Gradle builds. If you’re using an old version of Gradle, you’re missing out on the benefits of that work. Try upgrading to the latest version of Gradle to see what kind of impact it has. Doing so is low risk because...

Often times you will have reason to catch when your program is being told to stop by the OS and take some actions to preserve the state, or clean up your application. To accomplish this you can use the os/signal package from the standard library. Below is a simple example of assigning all signals fr...

Currently it contains rules for following libraries:- ButterKnife RxJava Android Support Library Android Design Support Library Retrofit Gson and Jackson Otto Crashlitycs Picasso Volley OkHttp3 Parcelable #Butterknife -keep class butterknife.** { *; } -keepnames class * { @butterk...

Checkboxes <%= check_box_tag(:pet_dog) %> <%= label_tag(:pet_dog, "I own a dog") %> <%= check_box_tag(:pet_cat) %> <%= label_tag(:pet_cat, "I own a cat") %> This will generate the following html <input id="pet_dog" name="pet_dog&q...

Browser support for ES6 is growing, but to be sure your code will work on environments that dont fully support it, you can use Babel, the ES6/7 to ES5 transpiler, try it out! If you would like to use ES6/7 in your projects without having to worry about compatibility, you can use Node and Babel CLI ...

Required Namespace: System.Security.Cryptography private class Encryption { private const string SecretKey = "topSecretKeyusedforEncryptions"; private const string SecretIv = "secretVectorHere"; public string Encrypt(string data...

PROGRAM zhello_world. CLASS main DEFINITION FINAL CREATE PRIVATE. PUBLIC SECTION. CLASS-METHODS: start. ENDCLASS. CLASS main IMPLEMENTATION. METHOD start. cl_demo_output=>display( 'Hello World!' ). ENDMETHOD. ENDCLASS. START-OF-SELECTION. main=>start( ).

To enable - type: :set number or :set nu. To disable - type: :set nonumber or :set nonu. To enable enumerating relative to the cursor location - type: :set relativenumber. To disable enumerating relative to the cursor location - type: :set norelativenumber. Note: To change whether the curren...

If you don't need automatically generated apk files with unaligned suffix (which you probably don't), you may add the following code to build.gradle file: // delete unaligned files android.applicationVariants.all { variant -> variant.assemble.doLast { variant.outputs.each { output ->...

The Composite pattern is a design pattern that allows to treat a group of objects as a single instance of an object. It is one of the Gang of Four's structural design patterns. Example below demonstrate how Composite can be used to log to multiple places using single Log invocation. This approach a...