Saturday, February 4, 2017

Objective-C Classes & Objects

The main purpose of Objective-C programming language is to add object orientation to the C programming language and classes are the central feature of Objective-C that support object-oriented programming and are often called user-defined types.

Objective-C Inheritance

One of the most important concepts in object-oriented programming is that of inheritance. Inheritance allows us to define a class in terms of another class which makes it easier to create and maintain an application. This also provides an opportunity to reuse the code functionality and fast implementation time.

Objective-C Polymorphism

The word polymorphism means having many forms. Typically, polymorphism occurs when there is a hierarchy of classes and they are related by inheritance.
Objective-C polymorphism means that a call to a member function will cause a different function to be executed depending on the type of object that invokes the function.

Objective-C Data Encapsulation

All Objective-C programs are composed of the following two fundamental elements:

Program statements (code): This is the part of a program that performs actions and they are called methods.
Program data: The data is the information of the program which is affected by the program functions.

Objective-C Categories

Sometimes, you may find that you wish to extend an existing class by adding behavior that is useful only in certain situations. In order add such extension to existing classes, Objective-C provides categories and extensions.

Objective-C Posing

Before starting about Posing in Objective-C, I would like to bring to your notice that Posing was declared deprecated in Mac OS X 10.5 and it's not available for use thereafter. So for those who are not concerned about these deprecated methods can skip this chapter.

Objective-C Extensions

A class extension bears some similarity to a category, but it can only be added to a class for which you have the source code at compile time (the class is compiled at the same time as the class extension).
The methods declared by a class extension are implemented in the implementation block for the original class, so you can't,

Objective-C Protocols

Objective-C allows you to define protocols, which declare the methods expected to be used for a particular situation. Protocols are implemented in the classes conforming to the protocol.
A simple example would be a network URL handling class, it will have a protocol with methods like processCompleted delegate method that intimates the calling class once the network URL fetching operation is over.

Objective-C Dynamic Binding

Dynamic binding is determining the method to invoke at runtime instead of at compile time. Dynamic binding is also referred to as late binding.
In Objective-C, all methods are resolved dynamically at runtime. The exact code executed is determined by both the method name (the selector) and the receiving object.

Objective-C Composite Objects

We can create subclass within a class cluster that defines a class that embeds within it an object. These class objects are composite objects.
So you might be wondering what's a class cluster. So we will first see what's a class cluster.

Obj-C Foundation Framework

If you refer Apple documentation, you can see the details of Foundation framework as given below.
The Foundation framework defines a base layer of Objective-C classes. In addition to providing a set of useful primitive object classes, it introduces several paradigms that define functionality not covered by the Objective-C language. The Foundation framework is designed with these goals in mind:

Objective-C Fast Enumeration

Fast enumeration is an Objective-C's feature that helps in enumerating through a collection. So in order to know about fast enumeration, we need know about collection first which will be explained in the following section.

Obj-C Memory Management

Memory management is one of the most important process in any programming language. It is the process by which the memory of objects are allocated when they are required and deallocated when they are no longer required.

Objective-C Overview

Objective-C is general-purpose language that is developed on top of C Programming language by adding features of Small Talk programming language making it an object-oriented language. It is primarily used in developing iOS and Mac OS X operating systems as well as its applications.

Objective-C - Useful Resources

The following resources contain additional information on Objective C. Please use them to get more in-depth knowledge on this topic.

Discuss Objective-C

Objective-C is a general-purpose, object-oriented programming language that adds Smalltalk-style messaging to the C programming language. This is the main programming language used by Apple for the OS X and iOS operating systems and their respective APIs, Cocoa and Cocoa Touch.

What is Node.js?

Node.js is a server-side platform built on Google Chrome's JavaScript Engine (V8 Engine). Node.js was developed by Ryan Dahl in 2009 and its latest version is v0.10.36. The definition of Node.js as supplied by its official documentation is as follows −

Try it Option Online
You really do not need to set up your own environment to start learning Node.js. Reason is very simple, we already have set up Node.js environment online, so that you can execute all the available examples online at the same time when you are doing your theory work.

Node.js - First Application

Before creating an actual "Hello, World!" application using Node.js, let us see the components of a Node.js application. A Node.js application consists of the following three important components −

Node.js - REPL Terminal

REPL stands for Read Eval Print Loop and it represents a computer environment like a Windows console or Unix/Linux shell where a command is entered and the system responds with an output in an interactive mode. Node.js or Node comes bundled with a REPL environment. It performs the following tasks −

Node.js - NPM

Node Package Manager (NPM) provides two main functionalities −

Online repositories for node.js packages/modules which are searchable on search.nodejs.org
Command line utility to install Node.js packages, do version management and dependency management of Node.js packages.

What is Callback?

Callback is an asynchronous equivalent for a function. A callback function is called at the completion of a given task. Node makes heavy use of callbacks. All the APIs of Node are written in such a way that they support callbacks.

Node.js - Event Loop

Node.js is a single-threaded application, but it can support concurrency via the concept of event and callbacks. Every API of Node.js is asynchronous and being single-threaded, they use async function calls to maintain concurrency.

Node.js - Event Emitter

Many objects in a Node emit events, for example, a net.Server emits an event each time a peer connects to it, an fs.readStream emits an event when the file is opened. All objects which emit events are the instances of events.EventEmitter.

Node.js - Buffers

Pure JavaScript is Unicode friendly, but it is not so for binary data. While dealing with TCP streams or the file system, it's necessary to handle octet streams. Node provides Buffer class which provides instances to store raw data similar to an array of integers but corresponds to a raw memory allocation outside the V8 heap.

What are Streams?

Streams are objects that let you read data from a source or write data to a destination in continuous fashion. In Node.js, there are four types of streams −

Node.js - File System

Node implements File I/O using simple wrappers around standard POSIX functions. The Node File System (fs) module can be imported using the following syntax −

var fs = require("fs")

Node.js - Global Objects

Node.js global objects are global in nature and they are available in all modules. We do not need to include these objects in our application, rather we can use them directly. These objects are modules, functions, strings and object itself as explained below.

Node.js - Utility Modules

There are several utility modules available in Node.js module library. These modules are very common and are frequently used while developing any Node based application.

What is a Web Server?

A Web Server is a software application which handles HTTP requests sent by the HTTP client, like web browsers, and returns web pages in response to the clients. Web servers usually deliver html documents along with images, style sheets, and scripts.

Express Overview

Express is a minimal and flexible Node.js web application framework that provides a robust set of features to develop web and mobile applications. It facilitates the rapid development of Node based Web applications. Following are some of the core features of Express framework −

What is REST architecture?

REST stands for REpresentational State Transfer. REST is web standards based architecture and uses HTTP Protocol. It revolves around resource where every component is a resource and a resource is accessed by a common interface using HTTP standard methods. REST was first introduced by Roy Fielding in 2000.

Node.js - Scaling Application

Node.js runs in a single-thread mode, but it uses an event-driven paradigm to handle concurrency. It also facilitates creation of child processes to leverage parallel processing on multi-core CPU based systems.
Child processes always have three streams child.stdin, child.stdout, and child.stderr which may be shared with the stdio streams of the parent process.

Node.js - Packaging

JXcore, which is an open source project, introduces a unique feature for packaging and encryption of source files and other assets into JX packages.
Consider you have a large project consisting of many files. JXcore can pack them all into a single file to simplify the distribution. This chapter provides a quick overview of the whole process starting from installing JXcore.

Node.js - Introduction

What is Node.js?

Node.js - Useful Resources

The following resources contain additional information on Node.js. Please use them to get more in-depth knowledge on this.

Discuss Node.js

Node.js is a very powerful JavaScript-based framework/platform built on Google Chrome's JavaScript V8 Engine. It is used to develop I/O intensive web applications like video streaming sites, single-page applications, and other web applications. Node.js is open source, completely free, and used by thousands of developers around the world.

MATLAB - Overview

MATLAB (matrix laboratory) is a fourth-generation high-level programming language and interactive environment for numerical computation, visualization and programming.

Try it Option Online
You really do not need to set up your own environment to start learning MATLAB Octave. Reason is very simple, we already have set up MATLAB Octave environment online, so that you can execute all the available examples online at the same time when you are doing your theory work.

MATLAB - Basic Syntax

MATLAB environment behaves like a super-complex calculator. You can enter commands at the >> command prompt.
MATLAB is an interpreted environment. In other words, you give a command and MATLAB executes it right away.

MATLAB - Variables

In MATLAB environment, every variable is an array or matrix.
You can assign variables in a simple way. For example,


x = 3        % defining x and initializing it with a value

MATLAB will execute the above statement and return the following result −

x = 3

MATLAB - Commands

MATLAB is an interactive program for numerical computation and data visualization. You can enter a command by typing it at the MATLAB prompt '>>' on the Command Window.
In this section, we will provide lists of commonly used general MATLAB commands.

MATLAB - M-Files

So far, we have used MATLAB environment as a calculator. However, MATLAB is also a powerful programming language, as well as an interactive computational environment.
In previous chapters, you have learned how to enter commands from the MATLAB command prompt.

MATLAB - Data Types

MATLAB does not require any type declaration or dimension statements. Whenever MATLAB encounters a new variable name, it creates the variable and allocates appropriate memory space.

MATLAB - Operators

An operator is a symbol that tells the compiler to perform specific mathematical or logical manipulations. MATLAB is designed to operate primarily on whole matrices and arrays. Therefore, operators in MATLAB work both on scalar and non-scalar data. MATLAB allows the following types of elementary operations −

MATLAB - Decision Making

Decision making structures require that the programmer should specify one or more conditions to be evaluated or tested by the program, along with a statement or statements to be executed if the condition is determined to be true, and optionally, other statements to be executed if the condition is determined to be false.

MATLAB - Matrix

A matrix is a two-dimensional array of numbers.
In MATLAB, you create a matrix by entering elements in each row as comma or space delimited numbers and using semicolons to mark the end of each row.
For example, let us create a 4-by-5 matrix a −

MATLAB - Loop Types

There may be a situation when you need to execute a block of code several number of times. In general, statements are executed sequentially. The first statement in a function is executed first, followed by the second, and so on.

MATLAB - Vectors

A vector is a one-dimensional array of numbers. MATLAB allows creating two types of vectors −

Row vectors
Column vectors

MATLAB - Arrays

All variables of all data types in MATLAB are multidimensional arrays. A vector is a one-dimensional array and a matrix is a two-dimensional array.
We have already discussed vectors and matrices. In this chapter, we will discuss multidimensional arrays. However, before that, let us discuss some special types of arrays.

MATLAB - Colon Notation

The colon(:) is one of the most useful operator in MATLAB. It is used to create vectors, subscript arrays, and specify for iterations.
If you want to create a row vector, containing integers from 1 to 10, you write −

MATLAB - Numbers

MATLAB supports various numeric classes that include signed and unsigned integers and single-precision and double-precision floating-point numbers. By default, MATLAB stores all numeric values as double-precision floating point numbers.

MATLAB - Strings

Creating a character string is quite simple in MATLAB. In fact, we have used it many times. For example, you type the following in the command prompt −

MATLAB - Functions

A function is a group of statements that together perform a task. In MATLAB, functions are defined in separate files. The name of the file and of the function should be the same.

MATLAB - Data Import

Importing data in MATLAB means loading data from an external file. The importdata function allows loading various data files of different formats. It has the following five forms −

MATLAB - Data Output

Data export (or output) in MATLAB means to write into files. MATLAB allows you to use your data in another application that reads ASCII files. For this, MATLAB provides several data export options.
You can create the following type of files:

MATLAB - Plotting

To plot the graph of a function, you need to take the following steps −

Define x, by specifying the range of values for the variable x, for which the function is to be plotted
Define the function, y = f(x)
Call the plot command, as plot(x, y)

MATLAB - Graphics

This chapter will continue exploring the plotting and graphics capabilities of MATLAB. We will discuss −

Drawing bar charts
Drawing contours
Three dimensional plots

MATLAB - Algebra

So far, we have seen that all the examples work in MATLAB as well as its GNU, alternatively called Octave. But for solving basic algebraic equations, both MATLAB and Octave are little different, so we will try to cover MATLAB and Octave in separate sections.

MATLAB - Calculus

MATLAB provides various ways for solving problems of differential and integral calculus, solving differential equations of any degree and calculation of limits. Best of all, you can easily plot the graphs of complex functions and check maxima, minima and other stationery points on a graph by solving the original function, as well as its derivative.

MATLAB - Differential

MATLAB provides the diff command for computing symbolic derivatives. In its simplest form, you pass the function you want to differentiate to diff command as an argument.
For example, let us compute the derivative of the function f(t) = 3t² + 2t^-2

MATLAB - Integration

Integration deals with two essentially different types of problems.

In the first type, derivative of a function is given and we want to find the function. Therefore, we basically reverse the process of differentiation. This reverse process is known as anti-differentiation, or finding the primitive function, or finding an indefinite integral.

MATLAB - Polynomials

MATLAB represents polynomials as row vectors containing coefficients ordered by descending powers. For example, the equation P(x) = x⁴ + 7x³ - 5x + 9 could be represented as −
p = [1 7 0 -5 9];

MATLAB - Transforms

MATLAB provides command for working with transforms, such as the Laplace and Fourier transforms. Transforms are used in science and engineering as a tool for simplifying analysis and look at data from another angle.

MATLAB - GNU Octave Tutorial

GNU Octave is a high-level programming language like MATLAB and it is mostly compatible with MATLAB. It is also used for numerical computations.
Octave has the following common features with MATLAB −

MATLAB - Simulink

Simulink is a simulation and model-based design environment for dynamic and embedded systems, integrated with MATLAB. Simulink, also developed by MathWorks, is a data flow graphical programming language tool for modelling, simulating and analyzing multi-domain dynamic systems.

MATLAB - Overview

MATLAB (matrix laboratory) is a fourth-generation high-level programming language and interactive environment for numerical computation, visualization and programming.

MATLAB is developed by MathWorks.

MATLAB - USeful Resources

The following resources contain additional information on MATLAB. Please use them to get more in-depth knowledge on this topic.

Discuss MATLAB

MATLAB is a programming language developed by MathWorks. It started out as a matrix programming language where linear algebra programming was simple. It can be run both under interactive sessions and as a batch job.

LISP - Overview

John McCarthy invented LISP in 1958, shortly after the development of FORTRAN. It was first implement by Steve Russell on an IBM 704 computer.

Try it Option Online
You really do not need to set up your own environment to start learning LISP programming language. Reason is very simple, we already have set up Lisp Programming environment online, so that you can execute all the available examples online at the same time when you are doing your theory work.

LISP - Program Structure

LISP expressions are called symbolic expressions or s-expressions. The s-expressions are composed of three valid objects, atoms, lists and strings.
Any s-expression is a valid program.

Basic Building Blocks in LISP

LISP programs are made up of three basic building blocks:

atom
list
string

LISP - Data Types

In LISP, variables are not typed, but data objects are.
LISP data types can be categorized as.

Scalar types - for example, number types, characters, symbols etc.
Data structures - for example, lists, vectors, bit-vectors, and strings.

LISP - Macros

Macros allow you to extend the syntax of standard LISP.
Technically, a macro is a function that takes an s-expression as arguments and returns a LISP form, which is then evaluated.

LISP - Variables

In LISP, each variable is represented by a symbol. The variable's name is the name of the symbol and it is stored in the storage cell of the symbol.

LISP - Constants

In LISP, constants are variables that never change their values during program execution. Constants are declared using the defconstant construct.

LISP - Operators

An operator is a symbol that tells the compiler to perform specific mathematical or logical manipulations. LISP allows numerous operations on data, supported by various functions, macros and other constructs.
The operations allowed on data could be categorized as:

LISP - Decision Making

Decision making structures require that the programmer specify one or more conditions to be evaluated or tested by the program, along with a statement or statements to be executed if the condition is determined to be true, and optionally, other statements to be executed if the condition is determined to be false.

LISP - Loops

There may be a situation, when you need to execute a block of code numbers of times. A loop statement allows us to execute a statement or group of statements multiple times and following is the general form of a loop statement in most of the programming languages.

LISP - Functions

A function is a group of statements that together perform a task.
You can divide up your code into separate functions. How you divide up your code among different functions is up to you, but logically the division usually is so each function performs a specific task.

LISP - Predicates

Predicates are functions that test their arguments for some specific conditions and returns nil if the condition is false, or some non-nil value is the condition is true.
The following table shows some of the most commonly used predicates:

LISP - Numbers

Common Lisp defines several kinds of numbers. The number data type includes various kinds of numbers supported by LISP.
The number types supported by LISP are:

LISP - Characters

In LISP, characters are represented as data objects of type character.
You can denote a character object preceding #\ before the character itself. For example, #\a means the character a.

LISP - Arrays

LISP allows you to define single or multiple-dimension arrays using the make-array function. An array can store any LISP object as its elements.
All arrays consist of contiguous memory locations. The lowest address corresponds to the first element and the highest address to the last element.

LISP - Strings

Strings in Common Lisp are vectors, i.e., one-dimensional array of characters.
String literals are enclosed in double quotes. Any character supported by the character set can be enclosed within double quotes to make a string, except the double quote character (") and the escape character (\). However, you can include these by escaping them with a backslash (\).

LISP - Sequences

Sequence is an abstract data type in LISP. Vectors and lists are the two concrete subtypes of this data type. All the functionalities defined on sequence data type are actually applied on all vectors and list types.
In this section, we will discuss most commonly used functions on sequences.

LISP - Lists

Lists had been the most important and the primary composite data structure in traditional LISP. Present day's Common LISP provides other data structures like, vector, hash table, classes or structures.
Lists are single linked lists. In LISP, lists are constructed as a chain of a simple record structure named cons linked together.

LISP - Symbols

In LISP, a symbol is a name that represents data objects and interestingly it is also a data object.
What makes symbols special is that they have a component called the property list, or plist.

LISP - Vectors

Vectors are one-dimensional arrays, therefore a subtype of array. Vectors and lists are collectively called sequences. Therefore all sequence generic functions and array functions we have discussed so far, work on vectors.

LISP - Set

Common Lisp does not provide a set data type. However, it provides number of functions that allows set operations to be performed on a list.
You can add, remove, and search for items in a list, based on various criteria. You can also perform various set operations like: union, intersection, and set difference.

LISP - Tree

You can build tree data structures from cons cells, as lists of lists.
To implement tree structures, you will have to design functionalities that would traverse through the cons cells, in specific order, for example, pre-order, in-order, and post-order for binary trees.

LISP - Hash Table

The hash table data structure represents a collection of key-and-value pairs that are organized based on the hash code of the key. It uses the key to access the elements in the collection.

LISP - Input & Output

Common LISP provides numerous input-output functions. We have already used the format function, and print function for output. In this section, we will look into some of the most commonly used input-output functions provided in LISP.

LISP - File I/O

We have discussed about how standard input and output is handled by common LISP. All these functions work for reading from and writing into text and binary files too. Only difference is in this case the stream we use is not standard input or output, but a stream created for the specific purpose of writing into or reading from files.

LISP - Structures

Structures are one of the user-defined data type, which allows you to combine data items of different kinds.
Structures are used to represent a record. Suppose you want to keep track of your books in a library. You might want to track the following attributes about each book:

LISP - Packages

In general term of programming languages, a package is designed for providing a way to keep one set of names separate from another. The symbols declared in one package will not conflict with the same symbols declared in another. This way packages reduce the naming conflicts between independent code modules.

LISP - Error Handling

In Common LISP terminology, exceptions are called conditions.
In fact, conditions are more general than exceptions in traditional programming languages, because a condition represents any occurrence, error, or not, which might affect various levels of function call stack.

LISP - CLOS

Common LISP predated the advance of object-oriented programming by couple of decades. However, it object-orientation was incorporated into it at a later stage.

LISP - Overview

John McCarthy invented LISP in 1958, shortly after the development of FORTRAN. It was first implement by Steve Russell on an IBM 704 computer.
It is particularly suitable for Artificial Intelligence programs, as it processes symbolic information effectively.

LISP - Useful Resources

The following resources contain additional information on LISP. Please use them to get more in-depth knowledge on this topic.

Discuss LISP

Lisp is the second-oldest high-level programming language after Fortran and has changed a great deal since its early days, and a number of dialects have existed over its history. Today, the most widely known general-purpose Lisp dialects are Common Lisp and Scheme.

Small & Simple Programs in C

Let's first start with very small & simple programs to get basic idea of C programming code structure. We shall get the basic idea of variable declaration, scanning and printing etc.

Loop Examples in C

This segment is designed to give the learner an enhanced view of how loops work in c langauges. We shall see simple loops like for, while and do-while, along with nested loops.

Patterns Examples in C

This section is full of examples that uses nested loops in a controlled manner. We may see that the outer loop is controlling the inner one etc. We have taken the simplest examples which are very common too.

Array Example Programs in C

Array is a collection of homogenous data, arranged in sequential format. Learning the concept of arrays in C is very important as it is the basic data structure. Here, in this section, we shall look into some very useful array programs to give you insight of how C programming language deals with arrays.

String Programs in C

Strings are actually one-dimensional array of characters terminated by a null character '\0'. Thus a null-terminated string contains the characters that comprise the string followed by a null.

Mathematical Programs in C

This section has been developed to introduce some common mathematical problems that can be solved using c programming language.

Linked List Programs in C

A linked-list is a sequence of data structures which are connected together via links.
Linked List is a sequence of links which contains items. Each link contains a connection to another link. Linked list the second most used data structure after array.

Small & Simple Programs in C

Let's first start with very small & small programs to get basic idea of C programming code structure. We shall get the basic idea of variable declaration, scanning and printing etc.

Learn C By Examples - Useful Resources

The following resources contain additional information on Learn C By Examples. Please use them to get more in-depth knowledge on this topic.

Discuss Learn C By Examples

C is a general-purpose, procedural, imperative computer programming language developed in 1972 by Dennis M. Ritchie at the Bell Telephone Laboratories to develop the UNIX operating system. C is the most widely used computer language. It keeps fluctuating at number one scale of popularity along with Java programming language, which is also equally popular and most widely used among modern software programmers.

JCL - Overview

When to use JCL

JCL is used in a mainframe environment to act as a communication between a program (Example: COBOL, Assembler or PL/I) and the operating system. In a mainframe environment, programs can be executed in batch and online mode.

Installing JCL on Windows/Linux

There are many Free Mainframe Emulators available for Windows which can be used to write and learn sample JCLs.
One such emulator is Hercules, which can be easily installed in Windows by following few simple steps given below:

JCL - JOB Statement

JOB Statement is the first control statement in a JCL. This gives the identity of the job to the Operating System (OS), in the spool and in the scheduler. The parameters in the JOB statement help the Operating Systems in allocating the right scheduler, required CPU time and issuing notifications to the user.

JCL - EXEC Statement

Each JCL can be made of many job steps. Each job step can execute a program directly or can call a procedure, which in turn executes one or more programs (job steps). The statement, which holds the job step program/procedure information is the EXEC statement.

JCL - DD Statement

Datasets are mainframe files with records organised in a specific format. Datasets are stored on the Direct Access Storage Device (DASD) or Tapes of the mainframe and are basic data storage areas. If these data are required to be used/created in a batch program, then the file (i.e., dataset) physical name along with the file format and organisation are coded in a JCL.

JCL - Base Library

Base Library is the Partitioned Dataset (PDS), which holds the load modules of the program to be executed in the JCL or the catalogued procedure, which is called in the program. Base libraries can be specified for the whole JCL in a JOBLIB library or for a particular job step in a STEPLIB statement.

JCL - Procedures

The JCL Procedures are set of statements inside a JCL grouped together to perform a particular function. Usually, the fixed part of the JCL is coded in a procedure. The varying part of the Job is coded within the JCL.

JCL - Conditional Processing

The Job Entry System uses two approaches to perform conditional processing in a JCL. When a job completes, a return code is set based on the status of execution. The return code can be a number between 0 (successful execution) to 4095 (non-zero shows error condition). The most common conventional values are:

JCL - Defining Datasets

A dataset name specifies the name of a file and it is denoted by DSN in JCL. The DSN parameter refers to the physical dataset name of a newly created or existing dataset. The DSN value can be made up of sub-names each of 1 to 8 characters length, separated by periods and of total length of 44 characters

Input-Output Methods

Any batch program executed through a JCL requires data input, which is processed and an output is created. There are different methods of feeding input to the program and writing output received from a JCL. In batch mode, there is no user interaction required but input and output devices and required organisation are defined in JCL and submitted.

Compiling COBOL Programs

In order to execute a COBOL program in batch mode using JCL, the program needs to be compiled and a load module is created with all the sub-programs. The JCL uses the load module and not the actual program at the time of execution.

IBM Dataset Utilities

Utility programs are pre-written programs, widely used in mainframes by system programmers and application developers to achieve day-to-day requirements, organising and maintaining data. A few of them are listed below with their functionality:

JCL - Basic Sort Tricks

The day-to-day application requirements in a corporate world that can be achieved using Utility Programs are illustrated below:

JCL Questions and Answers

JCL Questions and Answers has been designed with a special intention of helping students and professionals preparing for various Certification Exams and Job Interviews. This section provides a useful collection of sample Interview Questions and Multiple Choice Questions (MCQs) and their answers with appropriate explanations.

JCL - Overview

When to use JCL

JCL - Useful Resources

If you want to list down your website, book or any other resource on this page, then please contact at webmaster@tutorialspoint.com.

Discuss JCL

Job Control Language (JCL) is the command language of Multiple Virtual Storage (MVS), which is the commonly used Operating System in the IBM Mainframe computers. JCL identifies the program to be executed, the inputs that are required and location of the input/output and informs the Operating System through Job control Statements. In mainframe environment, programs can be executed in batch and online modes. JCL is used for submitting a program for execution in batch mode.

Java BeanUtils - Overview

Description

The Java BeanUtils are the components of the Apache Commons which are derived from JavaAPI and provides component architecture for the Java language. The Java BeanUtils design patterns uses utility classes that helps to get and set the property values on Java classes for retrieving and defining the bean properties.

Description

The standard JavaBeans of Java language can be used to access the property values of beans using the proper getter methods. The Java language supplies the java.beans.Introspector class to inspect a Java class at runtime.

Description

You can access the basic properties by using the following ways:

Simple Property
Indexed Property
Mapped Property

Description

You can access the value of nested property of the bean by concatenating the property names of the access path by using "." separators.
You can get and set the values of Nested property by using the below methods:

Description

The introspection tool can be used to learn about the properties and operations provided by your class. BeanUtils package is depending on JavaBeans specification that determines the available properties for a particular bean class.

Description

You can suppress the specific properties by using the bean introspection mechanism. The specialized BeanIntrospector interface is implemented by the type called SuppressPropertiesBeanIntrospector which suppresses the special class properties of Java beans.

Description

You can give dynamic property access on the existing JavaBean classes without altering with the help of PropertyUtils class. The dynamically calculated property values as JavaBean can also represented by using dynamic property access without writing a Java class to render these properties.

Description

The implementation of BasicDynaBean and BasicDynaClass specifies the capacity of dynamic property to provide the set of properties dynamically. You can start with DynaClass to establish the set of properties. A newInstance() method will create a new DynaBean instances to DynaClass and occupy its initial values as shown in the below example.

Description

The ResultSet can be wrapped in the DynaBeans by using the ResultSetDynaClass which renders the results of SQL query as series of DynaBeans. The most commonly used collection is java.sql.ResultSet which is returned when JDBC driver uses SQL SELECT statement.

Description

The RowSetDynaClass copies the undisclosed data in the DynaBeans memory while creating an instance which displays the result and using this class, you can close the ResultSet data before proceeding the actual data that was returned.

Description

As we have seen in the previous chapters, DynaBeans APIs provides get() and set() methods to access simple, indexed and mapped properties of DynaBeans dynamically.

Description

Lazy DynaBeans is an implementation of DynaBean, which gives the characteristics of Lazy List and Lazy Map this connects the properties of DynaClass. There are four types of Lazy DynaBeans:

Description

Data type conversion is a process of changing value from one data type to another. In the previous chapters, dynamically accessed properties of data types are recognized and to achieve the type conversions, we can use Java casts. The BeanUtils package gives various types of APIs and design patterns for performing the data type conversions.

Java BeanUtils - BeanUtils and ConvertUtils

Description

The BeanUtils is defined as a utility method for populating JavaBeans properties and ConvertUtils method converts string scalar values to objects, string arrays to arrays of the specified class.

Description

BeanUtils package allows creating your own string object to convert for any java class and the registered converters can be used by all the BeanUtils methods.
The following are the steps to create and register your own converter:

Description

The regular classes available in org.apache.commons.beanutils are not assigned for any specific event. These classes provide a clear interface to make use of situations very easily where the locale is not main thing. You can use Locale-aware extensions of beanutils classes which helps localization, from the org.apache.commons.beanutils.locale package.

Java BeanUtils - Utility Objects & Classes

Description

The utility classes such as BeanUtils, ConvertUtils and PropertyUtils can be accessed through utility objects and shares the same caches and registered converters. You can instantiate corresponding class with same functionality for each static utility class.

Description

In Apache Commons Beanutils, you can compare the JavaBean objects by using the BeanComparator class based on a specified shared property value. This can be done by using the org.apache.commons.beanutils.BeanComparator comparator.

Description

The Commons-Collections are build upon interfaces, implementations and utilities. It contains Closure interface in the code that can be applied on the arbitrary input object and code permits to apply Closures to contents of collection.

Description

The collections of beans can be filtered in the commons-collections by using the interface Predicate and also provides either true or false value on the evaluation of an input object. There is a Predicate called BeanPropertyValueEqualsPredicate which will assess the set property value against the given value.

Description

The conversion from input object to output object is supported in commons-collections with the help of Transformer interface. The Transformers can be applied to get the output collection from input collection with the help of codes available in Commons-collections.

Java 8 - Overview

JAVA 8 (aka jdk 1.8) is a major release of JAVA programming language development. Its initial version was released on 18 March 2014. With the Java 8 release, Java provided support for functional programming, new JavaScript engine, new APIs for date time manipulation, new streaming API, etc.

Try it Option Online
We have set up the Java Programming environment online, so that you can compile and execute all the available examples online. It gives you confidence in what you are reading and enables you to verify the programs with different options.

Java 8 - Lambda Expressions

Lambda expressions are introduced in Java 8 and are touted to be the biggest feature of Java 8. Lambda expression facilitates functional programming, and simplifies the development a lot.

Java 8 - Method References

Method references help to point to methods by their names. A method reference is described using :: (double colon) symbol. A method reference can be used to point the following types of methods −

Java 8 - Functional Interfaces

Functional interfaces have a single functionality to exhibit. For example, a Comparable interface with a single method ‘compareTo’ is used for comparison purpose. Java 8 has defined a lot of functional interfaces to be used extensively in lambda expressions. Following is the list of functional interfaces defined in java.util.Function package.

Java 8 - Default Methods

Java 8 introduces a new concept of default method implementation in interfaces. This capability is added for backward compatibility so that old interfaces can be used to leverage the lambda expression capability of Java 8.

Java 8 - Streams

Stream is a new abstract layer introduced in Java 8. Using stream, you can process data in a declarative way similar to SQL statements. For example, consider the following SQL statement −

SELECT max(salary), employee_id, employee_name FROM Employee

Java 8 - Optional Class

Optional is a container object which is used to contain not-null objects. Optional object is used to represent null with absent value. This class has various utility methods to facilitate code to handle values as ‘available’ or ‘not available’ instead of checking null values. It is introduced in Java 8 and is similar to what Optional is in Guava.

Class Declaration

Following is the declaration for java.util.Optional<T> class −

public final class Optional<T>
extends Object

Class Method

S. No.	Method & Description
1	static <T> Optional<T> empty() Returns an empty Optional instance.
2	boolean equals(Object obj) Indicates whether some other object is "equal to" this Optional.
3	Optional<T> filter(Predicate<? super <T> predicate) If a value is present and the value matches a given predicate, it returns an Optional describing the value, otherwise returns an empty Optional.
4	<U> Optional<U> flatMap(Function<? super T,Optional<U>> mapper) If a value is present, it applies the provided Optional-bearing mapping function to it, returns that result, otherwise returns an empty Optional.
5	T get() If a value is present in this Optional, returns the value, otherwise throws NoSuchElementException.
6	int hashCode() Returns the hash code value of the present value, if any, or 0 (zero) if no value is present.
7	void ifPresent(Consumer<? super T> consumer) If a value is present, it invokes the specified consumer with the value, otherwise does nothing.
8	boolean isPresent() Returns true if there is a value present, otherwise false.
9	<U>Optional<U> map(Function<? super T,? extends U> mapper) If a value is present, applies the provided mapping function to it, and if the result is non-null, returns an Optional describing the result.
10	static <T> Optional<T> of(T value) Returns an Optional with the specified present non-null value.
11	static <T> Optional<T> ofNullable(T value) Returns an Optional describing the specified value, if non-null, otherwise returns an empty Optional.
12	T orElse(T other) Returns the value if present, otherwise returns other.
13	T orElseGet(Supplier<? extends T> other) Returns the value if present, otherwise invokes other and returns the result of that invocation.
14	<X extends Throwable> T orElseThrow(Supplier<? extends X> exceptionSupplier) Returns the contained value, if present, otherwise throws an exception to be created by the provided supplier.
15	String toString() Returns a non-empty string representation of this Optional suitable for debugging.

Note − This class inherits methods from the java.lang.Object class.

Optional Example

To understand how Optional is used in practice, let us see the following example. Write the following program, execute and verify result to get more insight of it.

Java8Tester.java

import java.util.Optional;

public class Java8Tester {
   public static void main(String args[]){
   
      Java8Tester java8Tester = new Java8Tester();
      Integer value1 = null;
      Integer value2 = new Integer(10);
  
      //Optional.ofNullable - allows passed parameter to be null.
      Optional<Integer> a = Optional.ofNullable(value1);
  
      //Optional.of - throws NullPointerException if passed parameter is null
      Optional<Integer> b = Optional.of(value2);
      System.out.println(java8Tester.sum(a,b));
   }
 
   public Integer sum(Optional<Integer> a, Optional<Integer> b){
 
      //Optional.isPresent - checks the value is present or not
  
      System.out.println("First parameter is present: " + a.isPresent());
      System.out.println("Second parameter is present: " + b.isPresent());
  
      //Optional.orElse - returns the value if present otherwise returns
      //the default value passed.
      Integer value1 = a.orElse(new Integer(0));
  
      //Optional.get - gets the value, value should be present
      Integer value2 = b.get();
      return value1 + value2;
   }
}

Verify the Result

Compile the class using javac compiler as follows −

$javac Java8Tester.java

Now run the Java8Tester as follows −

$java Java8Tester

It should produce the following output −

First parameter is present: false
Second parameter is present: true
10

Java 8 - Nashorn JavaScript

With Java 8, Nashorn, a much improved javascript engine is introduced, to replace the existing Rhino. Nashorn provides 2 to 10 times better performance, as it directly compiles the code in memory and passes the bytecode to JVM. Nashorn uses invokedynamics feature, introduced in Java 7 to improve performance.

Java 8 - New Date/Time API

With Java 8, a new Date-Time API is introduced to cover the following drawbacks of old date-time API −

Not thread safe − java.util.Date is not thread safe, thus developers have to deal with concurrency issue while using date. The new date-time API is immutable and does not have setter methods.

Java 8 - Base64

With Java 8, Base64 has finally got its due. Java 8 now has inbuilt encoder and decoder for Base64 encoding. In Java 8, we can use three types of Base64 encoding −

Java 8 Questions and Answers

Java 8 Questions and Answers has been designed with a special intention of helping students and professionals preparing for various Certification Exams and Job Interviews. This section provides a useful collection of sample Interview Questions and Multiple Choice Questions (MCQs) and their answers with appropriate explanations.

Java 8 - Overview

JAVA 8 is a major feature release of JAVA programming language development. Its initial version was released on 18 March 2014. With the Java 8 release, Java provided supports for functional programming, new JavaScript engine, new APIs for date time manipulation, new streaming API, etc.

Java 8 - Useful Resources

The following resources contain additional information on Java8. Please use them to get more in-depth knowledge on this tpoic.

Discuss Java 8

Java 8 is the most awaited and is a major feature release of Java programming language. This is an introductory tutorial that explains the basic-to-advanced features of Java 8 and their usage in a simple and intuitive way.

Thursday, February 2, 2017

Groovy - Overview

Groovy - Environment

There are a variety of ways to get the Groovy environment setup.
Binary download and installation − Go to the link www.groovy-lang.org/download.html to get the Windows Installer section. Click on this option to start the download of the Groovy installer.

Groovy - Basic Syntax

In order to understand the basic syntax of Groovy, let’s first look at a simple Hello World program.

Creating Your First Hello World Program

Creating your first hello world program is as simple as just entering the following code line −

class Example {
   static void main(String[] args) {
      // Using a simple println statement to print output to the console
      println('Hello World');

Groovy - Data Types

In any programming language, you need to use various variables to store various types of information. Variables are nothing but reserved memory locations to store values. This means that when you create a variable you reserve some space in memory to store the value associated with the variable.

Groovy - Variables

Variables in Groovy can be defined in two ways − using the native syntax for the data type or the next is by using the def keyword. For variable definitions it is mandatory to either provide a type name explicitly or to use "def" in replacement. This is required by the Groovy parser.

Groovy - Operators

An operator is a symbol that tells the compiler to perform specific mathematical or logical manipulations.
Groovy has the following types of operators −

Arithmetic operators
Relational operators
Logical operators
Bitwise operators
Assignment operators

Groovy - Loops

So far, we have seen statements which have been executed one after the other in a sequential manner. Additionally, statements are provided in Groovy to alter the flow of control in a program’s logic. They are then classified into flow of control statements which we will see in detail.

Groovy - Decision Making

Decision-making structures require that the programmer specify one or more conditions to be evaluated or tested by the program, along with a statement or statements to be executed if the condition is determined to be true, and optionally, other statements to be executed if the condition is determined to be false.

Groovy - Methods

A method is in Groovy is defined with a return type or with the def keyword. Methods can receive any number of arguments. It’s not necessary that the types are explicitly defined when defining the arguments. Modifiers such as public, private and protected can be added. By default, if no visibility modifier is provided, the method is public.

Groovy - File I/O

Groovy provides a number of helper methods when working with I/O. Groovy provides easier classes to provide the following functionalities for files.

Reading files
Writing to files
Traversing file trees
Reading and writing data objects to files

Groovy - Optionals

Groovy is an “optionally” typed language, and that distinction is an important one when understanding the fundamentals of the language. When compared to Java, which is a “strongly” typed language, whereby the compiler knows all of the types for every variable and can understand and honor contracts at compile time. This means that method calls are able to be determined at compile time.

Groovy - Numbers

In Groovy, Numbers are actually represented as object’s, all of them being an instance of the class Integer. To make an object do something, we need to invoke one of the methods declared in its class.
Groovy supports integer and floating point numbers.

Groovy - Strings

A String literal is constructed in Groovy by enclosing the string text in quotations.
Groovy offers a variety of ways to denote a String literal. Strings in Groovy can be enclosed in single quotes (’), double quotes (“), or triple quotes (“””). Further, a Groovy String enclosed by triple quotes may span multiple lines.

Groovy - Ranges

A range is shorthand for specifying a sequence of values. A Range is denoted by the first and last values in the sequence, and Range can be inclusive or exclusive. An inclusive Range includes all the values from the first to the last, while an exclusive Range includes all values except the last. Here are some examples of Range literals −

Groovy - Lists

The List is a structure used to store a collection of data items. In Groovy, the List holds a sequence of object references. Object references in a List occupy a position in the sequence and are distinguished by an integer index. A List literal is presented as a series of objects separated by commas and enclosed in square brackets.

Groovy - Maps

A Map (also known as an associative array, dictionary, table, and hash) is an unordered collection of object references. The elements in a Map collection are accessed by a key value. The keys used in a Map can be of any class. When we insert into a Map collection, two values are required: the key and the value.
Following are some examples of maps −

Groovy - Dates & Times

The class Date represents a specific instant in time, with millisecond precision. The Date class has two constructors as shown below.

Groovy - Regular Expressions

A regular expression is a pattern that is used to find substrings in text. Groovy supports regular expressions natively using the ~”regex” expression. The text enclosed within the quotations represent the expression for comparison.

Groovy - Exception Handling

Exception handling is required in any programming language to handle the runtime errors so that normal flow of the application can be maintained.
Exception normally disrupts the normal flow of the application, which is the reason why we need to use Exception handling in our application.
Exceptions are broadly classified into the following categories −

Groovy - Object Oriented

In Groovy, as in any other Object-Oriented language, there is the concept of classes and objects to represent the objected oriented nature of the programming language. A Groovy class is a collection of data and the methods that operate on that data. Together, the data and methods of a class are used to represent some real world object from the problem domain.

Groovy - Generics

Generics enable types (classes and interfaces) to be parameters when defining classes, interfaces and methods. Much like the more familiar formal parameters used in method declarations, type parameters provide a way for you to re-use the same code with different inputs. The difference is that the inputs to formal parameters are values, while the inputs to type parameters are types.

Groovy - Traits

Traits are a structural construct of the language which allow −

Composition of behaviors.
Runtime implementation of interfaces.
Compatibility with static type checking/compilation

Groovy - Closures

A closure is a short anonymous block of code. It just normally spans a few lines of code. A method can even take the block of code as a parameter. They are anonymous in nature.
Following is an example of a simple closure and what it looks like.

Groovy - Annotations

Annotations are a form of metadata wherein they provide data about a program that is not part of the program itself. Annotations have no direct effect on the operation of the code they annotate.
Annotations are mainly used for the following reasons −

Groovy - XML

XML is a portable, open source language that allows programmers to develop applications that can be read by other applications, regardless of operating system and/or developmental language. This is one of the most common languages used for exchanging data between applications.

Groovy - JMX

JMX is the defacto standard which is used for monitoring all applications which have anything to do with the Java virual environment. Given that Groovy sits directly on top of Java, Groovy can leverage the tremendous amount of work already done for JMX with Java.

Groovy - JSON

This chapter covers how to we can use the Groovy language for parsing and producing JSON objects.

JSON Functions

Function	Libraries
JsonSlurper	JsonSlurper is a class that parses JSON text or reader content into Groovy data Structures such as maps, lists and primitive types like Integer, Double, Boolean and String.
JsonOutput	This method is responsible for serialising Groovy objects into JSON strings.

Groovy - DSLS

Groovy allows one to omit parentheses around the arguments of a method call for top-level statements. This is known as the "command chain" feature. This extension works by allowing one to chain such parentheses-free method calls, requiring neither parentheses around arguments, nor dots between the chained calls.

Groovy - Database

Groovy’s groovy-sql module provides a higher-level abstraction over the current Java’s JDBC technology. The Groovy sql API supports a wide variety of databases, some of which are shown below.

HSQLDB
Oracle
SQL Server
MySQL
MongoDB

Groovy - Builders

During the process of software development, sometimes developers spend a lot of time in creating Data structures, domain classes, XML, GUI Layouts, Output streams etc.And sometimes the code used to create these specific requirements results in the repitition of the same snippet of code in many places.

Groovy - Command Line

The Groovy shell known as groovysh can be easily used to evaluate groovy expressions, define classes and run simple programs. The command line shell gets installed when Groovy is installed.
Following are the command line options available in Groovy −

Groovy - Unit Testing

The fundamental unit of an object-oriented system is the class. Therefore unit testing consists of testig within a class. The approach taken is to create an object of the class under testing and use it to check that selected methods execute as expected. Not every method can be tested, since it is not always pratical to test each and every thing. But unit testing should be conducted for key and critical methods.

Groovy - Template Engines

Groovy’s template engine operates like a mail merge (the automatic addition of names and addresses from a database to letters and envelopes in order to facilitate sending mail, especially advertising, to many addresses) but it is much more general.

Groovy - Meta Object Programming

Meta object programming or MOP can be used to invoke methods dynamically and also create classes and methods on the fly.
So what does this mean? Let’s consider a class called Student, which is kind of an empty class with no member variables or methods.

Groovy - Overview

Groovy - Useful Resources

The following resources contain additional information on Groovy. Please use them to get more in-depth knowledge on this.

Discuss Groovy

Groovy is an object oriented language which is based on Java platform. Groovy 1.0 was released in January 2, 2007 with Groovy 2.4 as the current major release. Groovy is distributed via the Apache License v 2.0. In this tutorial, we would explain all the fundamentals of Groovy and how to put it into practice.

Go - Overview

Try it Option Online
You really do not need to set up your own environment to start learning Go programming language. Reason is very simple, we already have set up Go Programming environment online, so that you can compile and execute all the available examples online at the same time when you are doing your theory work.

Go - Program Structure

Before we study basic building blocks of the Go programming language, let us look a bare minimum Go program structure so that we can take it as a reference in upcoming chapters.

Go - Basic Syntax

You have seen a basic structure of Go program, so it will be easy to understand other basic building blocks of the Go programming language.

Go - Data Types

In the Go programming language, data types refer to an extensive system used for declaring variables or functions of different types. The type of a variable determines how much space it occupies in storage and how the bit pattern stored is interpreted.

Go - Variables

A variable is nothing but a name given to a storage area that our programs can manipulate. Each variable in Go has a specific type, which determines the size and layout of the variable's memory; the range of values that can be stored within that memory; and the set of operations that can be applied to the variable.

Go - Constants

The constants refer to fixed values that the program may not alter during its execution. These fixed values are also called literals.
Constants can be of any of the basic data types like an integer constant, a floating constant, a character constant, or a string literal. There are also enumeration constants as well.
The constants are treated just like regular variables except that their values cannot be modified after their definition.

Go - Operators

An operator is a symbol that tells the compiler to perform specific mathematical or logical manipulations. Go language is rich in built-in operators and provides the following types of operators:

Arithmetic Operators
Relational Operators
Logical Operators
Bitwise Operators
Assignment Operators
Misc Operators

Go - Decision Making

Go - Loops

There may be a situation, when you need to execute a block of code several number of times. In general, statements are executed sequentially: The first statement in a function is executed first, followed by the second, and so on.

Go - Functions

A function is a group of statements that together perform a task. Every Go program has at least one function, which is main(), and all the most trivial programs can define additional functions.

Go - Scope Rules

A scope in any programming is a region of the program where a defined variable can have its existence and beyond that variable can not be accessed. There are three places where variables can be declared in C programming language:

Go - Arrays

Go programming language provides a data structure called the array, which can store a fixed-size sequential collection of elements of the same type. An array is used to store a collection of data, but it is often more useful to think of an array as a collection of variables of the same type.

Go - Pointers

Pointers in Go are easy and fun to learn. Some Go programming tasks are performed more easily with pointers, and other tasks, such as call by reference, cannot be performed without using pointers. So it becomes necessary to learn pointers to become a perfect Go programmer. Let's start learning them in simple and easy steps.

Go - Structures

Go arrays allow you to define type of variables that can hold several data items of the same kind but structure is another user defined data type available in Go programming, which allows you to combine data items of different kinds.

Go - Slices

Go Slice is an abstraction over Go Array. As Go Array allows you to define type of variables that can hold several data items of the same kind but it do not provide any inbuilt method to increase size of it dynamically or get a sub-array of its own. Slices covers this limitation. It provides many utility functions required on Array and is widely used in Go programming.

Go - Range

The range keyword is used in for loop to iterate over items of an array, slice, channel or map. With array and slices, it returns the index of the item as integer. With maps, it returns the key of the next key-value pair. Range either returns one value or two. If only one value is used on the left of a range expression, it is the 1st value in the following table.

Go - Maps

Go provides another important data type map which maps unique keys to values. A key is an object that you use to retrieve a value at a later date. Given a key and a value, you can strore the value in a Map object. After value is stored, you can retrieve it by using its key.

Go - Recursion

Recursion is the process of repeating items in a self-similar way. Same applies in programming languages as well where if a programming allows you to call a function inside the same function that is called recursive call of the function as follows.

Go - Type Casting

Type casting is a way to convert a variable from one data type to another data type. For example, if you want to store a long value into a simple integer then you can type cast long to int. You can convert values from one type to another using the cast operator as following:

Go - Interfaces

Go programming provides another data type called interfaces which represents a set of method signatures. struct data type implements these interfaces to have metho definitions for the method signature of the interfaces.

Go - Error Handling

Go programming provides a pretty simple error handling framework with inbuit error interface type of following declaration:

type error interface {
   Error() string
}

Go Questions and Answers

Go Questions and Answers has been designed with a special intention of helping students and professionals preparing for various Certification Exams and Job Interviews. This section provides a useful collection of sample Interview Questions and Multiple Choice Questions (MCQs) and their answers with appropriate explanations.

Go - Overview

Go is a general-purpose language designed with systems programming in mind.It was initially developed at Google in year 2007 by Robert Griesemer, Rob Pike, and Ken Thompson. It is strongly and statically typed, provides inbuilt support for garbage collection and supports concurrent programming. Programs are constructed using packages, for efficient management of dependencies. Go programming implementations use a traditional compile and link model to generate executable binaries.

Go - Useful Resources

If you want to list down your website, book or any other resource on this page then please contact at webmaster@tutorialspoint.com

Discuss Go

Go language, is a programming language initially developed at Google in year 2007 by Robert Griesemer, Rob Pike, and Ken Thompson. Go programming language is a statically-typed language with syntax similar to that of C. It provides garbage collection, type safety, dynamic-typing capability, many advanced built-in types such as variable length arrays and key-value maps. It also provides a rich standard library. The Go programming language was announced in November 2009 and is used in some of the Google's production systems.

F# - Overview

F# is a functional programming language. To understand F# constructs, you need to read a couple of lines about the programming paradigm named Functional Programming.
Functional programming treats computer programs as mathematical functions.

F# - Environment Setup

The tools required for F# programming are discussed in this chapter.

Integrated Development Environment(IDE) for F#

Microsoft provides Visual Studio 2013 for F# programming.
The free Visual Studio 2013 Community Edition is available from Microsoft’s official website. Visual Studio 2013 Community and above comes with the Visual F# Tools.

F# - Program Structure

F# is a Functional Programming language.
In F#, functions work like data types. You can declare and use a function in the same way like any other variable.
In general, an F# application does not have any specific entry point. The compiler executes all top-level statements in the file from top to bottom.

F# - Basic Syntax

You have seen the basic structure of an F# program, so it will be easy to understand other basic building blocks of the F# programming language.

F# - Data Types

The data types in F# can be classified as follows −

Integral types
Floating point types
Text types
Other types

F# - Variables

A variable is a name given to a storage area that our programs can manipulate. Each variable has a specific type, which determines the size and layout of the variable's memory; the range of values that can be stored within that memory; and the set of operations that can be applied to the variable.

F# - Operators

An operator is a symbol that tells the compiler to perform specific mathematical or logical manipulations. F# is rich in built-in operators and provides the following types of operators −

Arithmetic Operators
Comparison Operators
Boolean Operators
Bitwise Operators

F# - Decision Making

Decision making structures require that the programmer specify one or more conditions to be evaluated or tested by the program. It should be along with a statement or statements to be executed if the condition is determined to be true, and optionally, other statements to be executed if the condition is determined to be false.

F# - Loops

Programming languages provide various control structures that allow for more complicated execution paths.
A loop statement allows us to execute a statement or group of statements multiple times and following is the general form of a loop statement in most of the programming languages −

F# - Functions

In F#, functions work like data types. You can declare and use a function in the same way like any other variable.
Since functions can be used like any other variables, you can −

F# - Strings

In F#, the string type represents immutable text as a sequence of Unicode characters.

String Literals

String literals are delimited by the quotation mark (") character.
Some special characters are there for special uses like newline, tab, etc. They are encoded using backslash (\) character. The backslash character and the related character make the escape sequence. The following table shows the escape sequence supported by F#.

F# - Options

The option type in F# is used in calculations when there may or may not exist a value for a variable or function. Option types are used for representing optional values in calculations. They can have two possible values − Some(x) or None.

F# - Tuples

A tuple is a comma-separated collection of values. These are used for creating ad hoc data structures, which group together related values.
For example, (“Zara Ali”, “Hyderabad”, 10) is a 3-tuple with two string values and an int value, it has the type (string * string * int).

F# - Records

A record is similar to a tuple, however it contains named fields. For example,

type website =
   { title : string;
      url : string }

Defining Record

F# - Lists

In F#, a list is an ordered, immutable series of elements of the same type. It is to some extent equivalent to a linked list data structure.
The F# module, Microsoft.FSharp.Collections.List, has the common operations on lists. However F# imports this module automatically and makes it accessible to every F# application.

F# - Sequences

Sequences, like lists also represent an ordered collection of values. However, the elements in a sequence or sequence expression are computed when required. They are not computed at once, and for this reason they are used to represent infinite data structures.

F# - Sets

A set in F# is a data structure that acts as a collection of items without preserving the order in which items are inserted. Sets do not allow duplicate entries to be inserted into the collection.

F# - Maps

In F#, a map is a special kind of set that associates the values with key. A map is created in a similar way as sets are created.

Creating Maps

Maps are created by creating an empty map using Map.empty and adding items using the Add function. The following example demonstrates this −

F# - Discriminated Unions

Unions, or discriminated unions allows you to build up complex data structures representing well-defined set of choices. For example, you need to build an implementation of a choice variable, which has two values yes and no. Using the Unions tool, you can design this.

F# - Mutable Data

Variables in F# are immutable, which means once a variable is bound to a value, it can’t be changed. They are actually compiled as static read-only properties.
The following example demonstrates this.

F# - Arrays

Arrays are fixed-size, zero-based, mutable collections of consecutive data elements that are all of the same type.

Creating Arrays

You can create arrays using various syntaxes and ways or by using the functions from the Array module. In this section, we will discuss creating arrays without using the module functions.
There are three syntactical ways of creating arrays without functions −

F# - Mutable Lists

The List<'T> class represents a strongly typed list of objects that can be accessed by index.
It is a mutable counterpart of the List class. It is similar to arrays, as it can be accessed by an index, however, unlike arrays, lists can be resized. Therefore you need not specify a size during declaration.

F# - Mutable Dictionary

The Dictionary<'TKey, 'TValue> class is the mutable analog of the F# map data structure and contains many of the same functions.
Recapitulating from the Map chapter in F#, a map is a special kind of set that associates the values with key.

F# - Basic I/O

Basic Input Output includes −

Reading from and writing into console.
Reading from and writing into file.

Core.Printf Module

We have used the printf and the printfn functions for writing into the console. In this section, we will look into the details of the Printf module of F#.

F# - Generics

Generics allow you to delay the specification of the data type of programming elements in a class or a method, until it is actually used in the program. In other words, generics allow you to write a class or method that can work with any data type.

F# - Delegates

A delegate is a reference type variable that holds the reference to a method. The reference can be changed at runtime. F# delegates are similar to pointers to functions, in C or C++.

F# - Enumerations

An enumeration is a set of named integer constants.
In F#, enumerations, also known as enums, are integral types where labels are assigned to a subset of the values. You can use them in place of literals to make code more readable and maintainable.

F# - Pattern Matching

Pattern matching allows you to “compare data with a logical structure or structures, decompose data into constituent parts, or extract information from data in various ways”.
In other terms, it provides a more flexible and powerful way of testing data against a series of conditions and performing some computations based on the condition met.
Conceptually, it is like a series of if… then statements.

F# - Exception Handling

An exception is a problem that arises during the execution of a program. An F# exception is a response to an exceptional circumstance that arises while a program is running, such as an attempt to divide by zero.
Exceptions provide a way to transfer control from one part of a program to another. F# exception handling provides the following constructs −

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