cycle is an infinite iterator.
>>> import itertools as it
>>> it.cycle('ABCD')
A B C D A B C D A B C D ...
Therefore, take care to give boundaries when using this to avoid an infinite loop. Example:
>>> # Iterate over each element in cycle for a fixed range
>&g...
When to use abstract classes: To implement the same or different behaviour among multiple related objects
When to use interfaces: to implement a contract by multiple unrelated objects
Abstract classes create "is a" relations while interfaces provide "has a" capability.
This c...
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
...
...
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 ...
If the value of the href-attribute begins with tel:, your device will dial the number when you click it. This works on mobile devices or on computers/tablets running software – like Skype or FaceTime – that can make phone calls.
<a href="tel:11234567890">Call us</a>
Most de...
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...
To declare a bean, simply annotate a method with the @Bean annotation or annotate a class with the @Component annotation (annotations @Service, @Repository, @Controller could be used as well).
When JavaConfig encounters such a method, it will execute that method and register the return value as a b...
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...
In molecular biology and genetics, GC-content (or guanine-cytosine content, GC% in short) is the percentage of nitrogenous bases on a DNA molecule that are either guanine or cytosine (from a possibility of four different ones, also including adenine and thymine).
Using BioPython:
>>> from...
Enabled directory index means that if someone access to any folder which don't contains index.php , index.html, index.htm or any other default file defined in DirectoryIndex in apache configuration then all files in that folder will be listed in browser if you try to visit that page.
Often director...
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
>...
