Tutorial by Examples: d

Place this code in a file named HelloWorld.scala: object Hello { def main(args: Array[String]): Unit = { println("Hello World!") } } Live demo To compile it to bytecode that is executable by the JVM: $ scalac HelloWorld.scala To run it: $ scala Hello When the Scala...
Program options can be handled with the getopt() function. It operates with a similar syntax to the POSIX getopt command, with additional support for GNU-style long options. #!/usr/bin/php // a single colon indicates the option takes a value // a double colon indicates the value may be omitted ...
Introduction HTML (Hypertext Markup Language) uses a markup system composed of elements which represent specific content. Markup means that with HTML you declare what is presented to a viewer, not how it is presented. Visual representations are defined by Cascading Style Sheets (CSS) and realized...
At the command line, first verify that you have Git installed: On all operating systems: git --version On UNIX-like operating systems: which git If nothing is returned, or the command is not recognized, you may have to install Git on your system by downloading and running the installer. See...
1/2 #=> 0 Since we are dividing two integers, the result is an integer. To solve this problem, we need to cast at least one of those to Float: 1.0 / 2 #=> 0.5 1.to_f / 2 #=> 0.5 1 / Float(2) #=> 0.5 Alternatively, fdiv may be used to return the floating point result of di...
Consider a database with the following two tables. Employees table: IdFNameLNameDeptId1JamesSmith32JohnJohnson4 Departments table: IdName1Sales2Marketing3Finance4IT Simple select statement * is the wildcard character used to select all available columns in a table. When used as a substitute f...
The JSONSerialization class is built into Apple's Foundation framework. 2.2 Read JSON The JSONObjectWithData function takes NSData, and returns AnyObject. You can use as? to convert the result to your expected type. do { guard let jsonData = "[\"Hello\", \"JSON\"]&q...
Enum cases can contain one or more payloads (associated values): enum Action { case jump case kick case move(distance: Float) // The "move" case has an associated distance } The payload must be provided when instantiating the enum value: performAction(.jump) performA...
Normally, enums can't be recursive (because they would require infinite storage): enum Tree<T> { case leaf(T) case branch(Tree<T>, Tree<T>) // error: recursive enum 'Tree<T>' is not marked 'indirect' } The indirect keyword makes the enum store its payload with...
Enums without payloads can have raw values of any literal type: enum Rotation: Int { case up = 0 case left = 90 case upsideDown = 180 case right = 270 } Enums without any specific type do not expose the rawValue property enum Rotation { case up case right cas...
Standard usage for (var i = 0; i < 100; i++) { console.log(i); } Expected output: 0 1 ... 99 Multiple declarations Commonly used to cache the length of an array. var array = ['a', 'b', 'c']; for (var i = 0; i < array.length; i++) { console.log(array[i]); } Expect...
Place the following code into a file name hello.go: package main import "fmt" func main() { fmt.Println("Hello, 世界") } Playground When Go is installed correctly this program can be compiled and run like this: go run hello.go Output: Hello, 世界 Once you are...
Using the def statement is the most common way to define a function in python. This statement is a so called single clause compound statement with the following syntax: def function_name(parameters): statement(s) function_name is known as the identifier of the function. Since a function def...
Decorators augment the behavior of other functions or methods. Any function that takes a function as a parameter and returns an augmented function can be used as a decorator. # This simplest decorator does nothing to the function being decorated. Such # minimal decorators can occasionally be used ...
As mentioned in the introduction, a decorator is a function that can be applied to another function to augment its behavior. The syntactic sugar is equivalent to the following: my_func = decorator(my_func). But what if the decorator was instead a class? The syntax would still work, except that now m...
Decorators normally strip function metadata as they aren't the same. This can cause problems when using meta-programming to dynamically access function metadata. Metadata also includes function's docstrings and its name. functools.wraps makes the decorated function look like the original function b...
A decorator takes just one argument: the function to be decorated. There is no way to pass other arguments. But additional arguments are often desired. The trick is then to make a function which takes arbitrary arguments and returns a decorator. Decorator functions def decoratorfactory(message): ...
The math module contains the math.sqrt()-function that can compute the square root of any number (that can be converted to a float) and the result will always be a float: import math math.sqrt(9) # 3.0 math.sqrt(11.11) # 3.3331666624997918 math.sqrt(Decimal('6.25')) ...
Sometimes you don't want to have your function accessible/stored as a variable. You can create an Immediately Invoked Function Expression (IIFE for short). These are essentially self-executing anonymous functions. They have access to the surrounding scope, but the function itself and any internal va...
A Promise object represents an operation which has produced or will eventually produce a value. Promises provide a robust way to wrap the (possibly pending) result of asynchronous work, mitigating the problem of deeply nested callbacks (known as "callback hell"). States and control flow ...

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