sudo apt-add-repository ppa:brightbox/ruby-ng
Hit Enter to confirm
sudo apt-get update
Then you can install your ruby version of choice (the ppa supports ruby2.0 ruby2.1 ruby2.2 ruby2.3 and legacy versions ruby1.8 ruby1.9.1) Don't forget to include the respective -dev package for your version. Ot...
Disclaimer: In no way does this example advocate the use of singletons. Singletons are to be used with a lot of care.
In PHP there is quite a standard way of implementing a singleton:
public class Singleton {
private $instance;
private function __construct() { };
public function...
With implicit keys:
key: value
another key:
- some
- more
- values
[1, 2, 3]: last value, which has a flow style key
With implicit and explicit keys:
? key
: value
another key:
- some
- more
- values
? [1, 2, 3]
: last value, which has a flow style key
key, another ...
To see all the facts involving the le relation from the prelude:
Coq < Search le.
le_n: forall n : nat, n <= n
le_S: forall n m : nat, n <= m -> n <= S m
...
max_l: forall n m : nat, m <= n -> Nat.max n m = n
max_r: forall n m : nat, n <= m -> Nat.max n m = m
...
...
Search for all facts involving a pattern in an hypothesis or conclusion:
Coq < Search (_ + O).
plus_n_O: forall n : nat, n = n + 0
The _ character serves as a wildcard, it can be used multiple times:
Coq < Search (S _ <= _).
le_S_n: forall n m : nat, S n <= S m -> n <= m
le...
Session Types are a way to tell the compiler about the protocol you want to use to communicate between threads - not protocol as in HTTP or FTP, but the pattern of information flow between threads. This is useful since the compiler will now stop you from accidentally breaking your protocol and causi...
Let's say your launch activity is called MainActivity, in your app com.example.myapp.
In the manifest:
<activity
android:name=".MainActivity"
>
<intent-filter>
<action android:name="android.intent.action.MAIN"/>
...
Bridge pattern decouples abstraction from implementation so that both can vary independently. It has been achieved with composition rather than inheritance.
Bridge UML diagram from wikipedia:
You have four components in this pattern.
Abstraction: It defines an interface
RefinedAbstraction: It ...
The dimension attribute on an object specifies that that object is an array. There are, in Fortran 2008, five array natures:1
explicit shape
assumed shape
assumed size
deferred shape
implied shape
Take the three rank-1 arrays2
integer a, b, c
dimension(5) a ! Explicit shape (default ...
Gnuplot is able to generate a graphic from a script file which allows for a sequence of commands necessary to draw a graphic to be executed in sequence instead of type in manually.
For the purpose of this example we'll create a simple script to draw a sin(x).
Create a script file
Create a file si...
# example data
DT = data.table(iris)
DT[, Bin := cut(Sepal.Length, c(4,6,8))]
To apply the same summarizing function to every column by group, we can use lapply and .SD
DT[, lapply(.SD, median), by=.(Species, Bin)]
# Species Bin Sepal.Length Sepal.Width Petal.Length Petal.Width
# 1...
Setup Ruby On Rails on Ubuntu 16.04 Xenial Xerus
All commands should be run in Linux terminal (hotkey: Ctrl + Alt + T)
You need to install Ruby on your local machine in development environment.
The first step is to install some dependencies for Ruby.
sudo apt-get update
sudo apt-get install git...
JUnit is the leading testing framework used for testing Java code.
The class under test models a simple bank account, that charges a penalty when you go overdrawn.
public class BankAccount {
private int balance;
public BankAccount(int i){
balance = i;
}
public Bank...
java.lang.ref package provides reference-object classes, which support a limited degree of interaction with the garbage collector.
Java has four main different reference types. They are:
Strong Reference
Weak Reference
Soft Reference
Phantom Reference
1. Strong Reference
This is the usual...
Problem
There is a series of repeating elements in page that you need to know which one an event occurred on to do something with that specific instance.
Solution
Give all common elements a common class
Apply event listener to a class. this inside event handler is the matching selector elemen...
When expecting someone to reproduce an R code that has random elements in it, the set.seed() function becomes very handy.
For example, these two lines will always produce different output (because that is the whole point of random number generators):
> sample(1:10,5)
[1] 6 9 2 7 10
>...
