Tutorial by Examples: on

The steps of overload resolution are: Find candidate functions via name lookup. Unqualified calls will perform both regular unqualified lookup as well as argument-dependent lookup (if applicable). Filter the set of candidate functions to a set of viable functions. A viable function for whi...

Recursion can be defined as: A method that calls itself until a specific condition is met. An excellent and simple example of recursion is a method that will get the factorial of a given number: public int Factorial(int number) { return number == 0 ? 1 : n * Factorial(number - 1); } ...

Enums are iterable: class Color(Enum): red = 1 green = 2 blue = 3 [c for c in Color] # [<Color.red: 1>, <Color.green: 2>, <Color.blue: 3>]

The jsonlite package is a fast JSON parser and generator optimized for statistical data and the web. The two main functions used to read and write JSON are fromJSON() and toJSON() respecitively, and are designed to work with vectors, matrices and data.frames, and streams of JSON from the web. Creat...

Add this permission to the manifest file to use Bluetooth features in your application: <uses-permission android:name="android.permission.BLUETOOTH" /> If you need to initiate device discovery or manipulate Bluetooth settings, you also need to add this permission: <uses-permi...

<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"> <circle r="30" cx="100" cy="100" fill="#ff0000" stroke="#00ff00" /> <rect x="200" y="200" width="50&...

Count returns the number of elements in an IEnumerable<T>. Count also exposes an optional predicate parameter that allows you to filter the elements you want to count. int[] array = { 1, 2, 3, 4, 2, 5, 3, 1, 2 }; int n = array.Count(); // returns the number of elements in the array int x ...

To search for a string inside a string, there are several functions: indexOf( searchString ) and lastIndexOf( searchString ) indexOf() will return the index of the first occurrence of searchString in the string. If searchString is not found, then -1 is returned. var string = "Hello, World!&q...

Sometimes it is useful to have multiple validations use one condition. It can be easily achieved using with_options. class User < ApplicationRecord with_options if: :is_admin? do |admin| admin.validates :password, length: { minimum: 10 } admin.validates :email, presence: true end...

This type of association allows an ActiveRecord model to belong to more than one kind of model record. Common example: class Human < ActiveRecord::Base has_one :address, :as => :addressable end class Company < ActiveRecord::Base has_one :address, :as => :addressable end cl...

The idea here is to move the computationally intensive jobs to C (using special macros), independent of Python, and have the C code release the GIL while it's working. #include "Python.h" ... PyObject *pyfunc(PyObject *self, PyObject *args) { ... Py_BEGIN_ALLOW_THREADS //...

Sometimes repos will have commits that only adjust whitespace, for example fixing indentation or switching between tabs and spaces. This makes it difficult to find the commit where the code was actually written. git blame -w will ignore whitespace-only changes to find where the line really came fr...

Output can be restricted by specifying line ranges as git blame -L <start>,<end> Where <start> and <end> can be: line number git blame -L 10,30 /regex/ git blame -L /void main/, git blame -L 46,/void foo/ +offset, -offset (only for <end>) git blame -...

One of the uses of recursion is to navigate through a hierarchical data structure, like a file system directory tree, without knowing how many levels the tree has or the number of objects on each level. In this example, you will see how to use recursion on a directory tree to find all sub-directorie...

It is a good idea to maintain a web-scraping session to persist the cookies and other parameters. Additionally, it can result into a performance improvement because requests.Session reuses the underlying TCP connection to a host: import requests with requests.Session() as session: # all req...

While RODBC is restricted to Windows computers with compatible architecture between R and any target RDMS, one of its key flexibilities is to work with Excel files as if they were SQL databases. require(RODBC) con = odbcConnectExcel("myfile.xlsx") # open a connection to the Excel file s...

To get the value of the last result from your last expression in the console, use an underscore _. >>> 2 + 2 4 >>> _ 4 >>> _ + 6 10 This magic underscore value is only updated when using a python expression that results in a value. Defining functions or for loops ...

The console for the primary version of Python can usually be opened by typing py into your windows console or python on other platforms. $ py Python 3.4.3 (v3.4.3:9b73f1c3e601, Feb 24 2015, 22:44:40) [MSC v.1600 64 bit (AMD64)] on win32 Type "help", "copyright", "credits&...

You can set an environment variable called PYTHONSTARTUP for Python's console. Whenever you enter the Python console, this file will be executed, allowing for you to add extra functionality to the console such as importing commonly-used modules automatically. If the PYTHONSTARTUP variable was set t...

A simple static file server would look like this: package main import ( "net/http" ) func main() { muxer := http.NewServeMux() fileServerCss := http.FileServer(http.Dir("src/css")) fileServerJs := http.FileServer(http.Dir("src/js")) file...