Tutorial by Examples: me

Deploying an advanced project template to shared hosting is a bit trickier than a basic one because it has two webroots, which shared hosting webservers don't support. We will need to adjust the directory structure so frontend URL will be http://site.local and backend URL will be http://site.local/a...

Suppose you have defined the following Person class: public class Person { String name; int age; public Person (int age, String name) { this.age = age; this.name = name; } } If you instantiate a new Person object: Person person = new Person(25, &qu...

There is already a function sum(). As a result, if we name a variable with the same name sum = 1+3; and if we try to use the function while the variable still exists in the workspace A = rand(2); sum(A,1) we will get the cryptic error: Subscript indices must either be real positive integer...

Given a random vector v = rand(10,1); if you want the sum of its elements, do NOT use a loop s = 0; for ii = 1:10 s = s + v(ii); end but use the vectorized capability of the sum() function s = sum(v); Functions like sum(), mean(), prod() and others, have the ability to operate ...

Method overloading, also known as function overloading, is the ability of a class to have multiple methods with the same name, granted that they differ in either number or type of arguments. Compiler checks method signature for method overloading. Method signature consists of three things - Met...

Method overriding is the ability of subtypes to redefine (override) the behavior of their supertypes. In Java, this translates to subclasses overriding the methods defined in the super class. In Java, all non-primitive variables are actually references, which are akin to pointers to the location of...

Using reflection, a method of an object can be invoked during runtime. The example shows how to invoke the methods of a String object. import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; String s = "Hello World!"; // method without parameters // i...

Although not strictly required, it is highly recommended to start your project in a "virtual environment." A virtual environment is a container (a directory) that holds a specific version of Python and a set of modules (dependencies), and which does not interfere with the operating system'...

Often, we need to perform an operation over every element in a variadic template parameter pack. There are many ways to do this, and the solutions get easier to read and write with C++17. Suppose we simply want to print every element in a pack. The simplest solution is to recurse: C++11 void print...

An XML document is a text file that conforms to the XML specification's well-formedness rules. Such a conforming document is said to be well-formed (not to be confused with valid). XML is very strict with well-formedness in comparison to other languages such as HTML. A text file that is not well-for...

traverse_ executes an Applicative action for every element in a Foldable structure. It ignores the action's result, keeping only the side-effects. (For a version which doesn't discard results, use Traversable.) -- using the Writer applicative functor (and the Sum monoid) ghci> runWriter $ trave...

Here is some sample XML against which example XPaths can be written: <r> <e a="1"/> <f a="2" b="1">Text 1</f> <f/> <g> <i c="2">Text 2</i> Text 3 <j>Text 4</j> </g&gt...

For the sample XML (without namespaces): This XPath, /r/e will select this element: <e a="1"/>

def say_hello_to(name) puts "Hello #{name}" end say_hello_to('Charles') # Hello Charles

def greet(greeting, name) puts "#{greeting} #{name}" end greet('Hi', 'Sophie') # Hi Sophie

def make_animal_sound(sound = 'Cuack') puts sound end make_animal_sound('Mooo') # Mooo make_animal_sound # Cuack It's possible to include defaults for multiple arguments: def make_animal_sound(sound = 'Cuack', volume = 11) play_sound(sound, volume) end make_animal_so...

def welcome_guests(*guests) guests.each { |guest| puts "Welcome #{guest}!" } end welcome_guests('Tom') # Welcome Tom! welcome_guests('Rob', 'Sally', 'Lucas') # Welcome Rob! # Welcome Sally! # W...

SQLiteOpenHelper is a helper class to manage database creation and version management. In this class, the onUpgrade() method is responsible for upgrading the database when you make changes to the schema. It is called when the database file already exists, but its version is lower than the one spec...

A common pattern in C, to easily imitate returning multiple values from a function, is to use pointers. #include <stdio.h> void Get( int* c , double* d ) { *c = 72; *d = 175.0; } int main(void) { int a = 0; double b = 0.0; Get( &a , &b ); pr...

Enums can define abstract methods, which each enum member is required to implement. enum Action { DODGE { public boolean execute(Player player) { return player.isAttacking(); } }, ATTACK { public boolean execute(Player player) { re...