Tutorial by Examples: o

Conditional Expression (or "The Ternary Operator")

The ternary operator is used for inline conditional expressions. It is best used in simple, concise operations that are easily read. The order of the arguments is different from many other languages (such as C, Ruby, Java, etc.), which may lead to bugs when people unfamiliar with Python's "s...

Python Language • Conditionals

Sample XML (without namespaces)

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...

xpath • Getting started with xpath

Implicit conversion

JavaScript will try to automatically convert variables to more appropriate types upon use. It's usually advised to do conversions explicitly (see other examples), but it's still worth knowing what conversions take place implicitly. "1" + 5 === "15" // 5 got converted to string. ...

JavaScript • Variable coercion/conversion

Comparison of different types

Python 2.x2.3 Objects of different types can be compared. The results are arbitrary, but consistent. They are ordered such that None is less than anything else, numeric types are smaller than non-numeric types, and everything else is ordered lexicographically by type. Thus, an int is less than a st...

Python Language • Incompatibilities moving from Python 2 to Python 3

Basic notation

Any type can be declared as an array using either the dimension attribute or by just indicating directly the dimension(s) of the array: ! One dimensional array with 4 elements integer, dimension(4) :: foo ! Two dimensional array with 4 rows and 2 columns real, dimension(4, 2) :: bar ! Three...

Fortran • Arrays

Optional parameter(s) (splat operator)

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...

Ruby Language • Methods

Basic String manipulation

fn main() { // Statically allocated string slice let hello = "Hello world"; // This is equivalent to the previous one let hello_again: &'static str = "Hello world"; // An empty String let mut string = String::new(); // An empty String ...

Rust • Strings

Traits to facilitate horizontal code reuse

Let's say we have an interface for logging: interface Logger { function log($message); } Now say we have two concrete implementations of the Logger interface: the FileLogger and the ConsoleLogger. class FileLogger implements Logger { public function log($message) { // Append...

PHP • Traits

Calling a function from another C file

foo.h #ifndef FOO_DOT_H /* This is an "include guard" */ #define FOO_DOT_H /* prevents the file from being included twice. */ /* Including a header file twice causes all kinds */ /* of interesting problems.*/ /** * This is a functi...

C Language • Declarations

Using a Global Variable

Use of global variables is generally discouraged. It makes your program more difficult to understand, and harder to debug. But sometimes using a global variable is acceptable. global.h #ifndef GLOBAL_DOT_H /* This is an "include guard" */ #define GLOBAL_DOT_H /** * This tells ...

C Language • Declarations

Getting and setting properties

Basic usage: PropertyInfo prop = myInstance.GetType().GetProperty("myProperty"); // get the value myInstance.myProperty object value = prop.GetValue(myInstance); int newValue = 1; // set the value myInstance.myProperty to newValue prop.setValue(myInstance, newValue); Setting rea...

C# Language • Reflection

onUpgrade() method

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...

Android • SQLite

Forcing a static constructor to be called

While static constructors are always called before the first usage of a type it's sometimes useful to be able to force them to be called and the RuntimeHelpers class provide an helper for it: using System.Runtime.CompilerServices; // ... RuntimeHelpers.RunClassConstructor(typeof(Foo).TypeHand...

C# Language • Constructors and Finalizers

Installation or Setup

To prepare your web site or web application to use Kendo UI, simply add the style and script files in the <head> section of your page. CDN services are provided for the minified versions of official Kendo UI releases, for both HTTP and HTTPS protocols. JQuery is also required to use Kendo UI...

kendo-ui • Getting started with kendo-ui

Singleton Class

What is a Singleton Class? A singleton class returns the same instance no matter how many times an application requests it. Unlike a regular class, A singleton object provides a global point of access to the resources of its class. When to Use Singleton Classes? Singletons are used in situations ...

Objective-C Language • Classes and Objects

Create a box-and-whisker plot with boxplot() {graphics}

This example use the default boxplot() function and the irisdata frame. > head(iris) Sepal.Length Sepal.Width Petal.Length Petal.Width Species 1 5.1 3.5 1.4 0.2 setosa 2 4.9 3.0 1.4 0.2 setosa 3 4.7 3.2 ...

R Language • boxplot

Creating a new program using Mono

First install Mono by going through the install instructions for the platform of your choice as described in their installation section. Mono is available for Mac OS X, Windows and Linux. After installation is done, create a text file, name it HelloWorld.cs and copy the following content into it: ...

C# Language • Getting started with C# Language

Drop Constraint

ALTER TABLE Employees DROP CONSTRAINT DefaultSalary This Drops a constraint called DefaultSalary from the employees table definition. Note:- Ensure that constraints of the column are dropped before dropping a column.

SQL • ALTER TABLE

Add Constraint

ALTER TABLE Employees ADD CONSTRAINT DefaultSalary DEFAULT ((100)) FOR [Salary] This adds a constraint called DefaultSalary which specifies a default of 100 for the Salary column. A constraint can be added at the table level. Types of constraints Primary Key - prevents a duplicate record in...

SQL • ALTER TABLE

Using pointer parameters to return multiple values

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...

C Language • Function Parameters