Lua Scripting Language (Tutorials Point) (Z-Library)

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i About the Tutorial Lua is an open source language built on top of C programming language. Lua has its value across multiple platforms ranging from large server systems to small mobile applications. This tutorial covers various topics ranging from the basics of Lua to its scope in various applications. Audience This tutorial is designed for all those readers who are looking for a starting point to learn Lua. It has topics suitable for both beginners as well as advanced users. Prerequisites It is a self-contained tutorial and you should be able to grasp the concepts easily even if you are a total beginner. However it would help if you have a basic understanding of working with a simple text editor and command line. Copyright & Disclaimer  Copyright 2015 by Tutorials Point (I) Pvt. Ltd. All the content and graphics published in this e-book are the property of Tutorials Point (I) Pvt. Ltd. The user of this e-book is prohibited to reuse, retain, copy, distribute or republish any contents or a part of contents of this e-book in any manner without written consent of the publisher. We strive to update the contents of our website and tutorials as timely and as precisely as possible, however, the contents may contain inaccuracies or errors. Tutorials Point (I) Pvt. Ltd. provides no guarantee regarding the accuracy, timeliness or completeness of our website or its contents including this tutorial. If you discover any errors on our website or in this tutorial, please notify us at contact@tutorialspoint.com

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ii Table of Contents About the Tutorial ..................................................................................................................................... i Audience .................................................................................................................................................... i Prerequisites .............................................................................................................................................. i Copyright & Disclaimer .............................................................................................................................. i Table of Contents ...................................................................................................................................... ii 1. OVERVIEW ............................................................................................................................ 1 Features .................................................................................................................................................... 1 How Lua is Implemented? ......................................................................................................................... 1 Learning Lua .............................................................................................................................................. 2 Some Uses of Lua ...................................................................................................................................... 2 2. ENVIRONMENT ..................................................................................................................... 3 Try it Option Online .................................................................................................................................. 3 Local Environment Setup .......................................................................................................................... 3 Text Editor ................................................................................................................................................ 3 The Lua Interpreter ................................................................................................................................... 4 The Lua Compiler ...................................................................................................................................... 4 Installation on Windows ........................................................................................................................... 4 Installation on Linux.................................................................................................................................. 4 Installation on Mac OS X ........................................................................................................................... 5 Lua IDE ...................................................................................................................................................... 5 3. BASIC SYNTAX ....................................................................................................................... 7 First Lua Program ...................................................................................................................................... 7 Tokens in Lua ............................................................................................................................................ 8 Comments ................................................................................................................................................ 9

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iii Identifiers ................................................................................................................................................. 9 Keywords .................................................................................................................................................. 9 Whitespace in Lua ................................................................................................................................... 10 4. VARIABLES .......................................................................................................................... 11 Variable Definition in Lua ........................................................................................................................ 11 Variable Declaration in Lua ..................................................................................................................... 12 Lvalues and Rvalues in Lua ...................................................................................................................... 13 5. DATA TYPES ........................................................................................................................ 14 Type Function ......................................................................................................................................... 14 6. OPERATORS ........................................................................................................................ 16 Arithmetic Operators .............................................................................................................................. 16 Relational Operators ............................................................................................................................... 17 Logical Operators .................................................................................................................................... 20 Misc Operators ....................................................................................................................................... 22 Operators Precedence in Lua .................................................................................................................. 22 7. LOOPS ................................................................................................................................. 25 while loop ............................................................................................................................................... 26 for loop ................................................................................................................................................... 27 repeat...until loop ................................................................................................................................... 29 nested loops ........................................................................................................................................... 31 Loop Control Statement .......................................................................................................................... 32 break statement ..................................................................................................................................... 33 The Infinite Loop ..................................................................................................................................... 34 8. DECISION MAKING .............................................................................................................. 35 if statement ............................................................................................................................................ 36

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iv if...else statement ................................................................................................................................... 37 The if...else if...else Statement ................................................................................................................ 39 nested if statements ............................................................................................................................... 40 9. FUNCTIONS ......................................................................................................................... 42 Defining a Function ................................................................................................................................. 42 Function Arguments ................................................................................................................................ 43 Calling a Function .................................................................................................................................... 43 Assigning and Passing Functions ............................................................................................................. 44 Function with Variable Argument ........................................................................................................... 45 10. STRINGS .............................................................................................................................. 46 String Manipulation ................................................................................................................................ 47 Case Manipulation .................................................................................................................................. 48 Replacing a Substring .............................................................................................................................. 48 Finding and Reversing ............................................................................................................................. 49 Formatting Strings .................................................................................................................................. 49 Character and Byte Representations ....................................................................................................... 50 Other Common Functions ....................................................................................................................... 51 11. ARRAYS ............................................................................................................................... 52 One-Dimensional Array ........................................................................................................................... 52 Multi-Dimensional Array ......................................................................................................................... 53 12. ITERATORS .......................................................................................................................... 56 Generic For Iterator ................................................................................................................................ 56 Stateless Iterators ................................................................................................................................... 56 Stateful Iterators ..................................................................................................................................... 58

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v 13. TABLES ................................................................................................................................ 60 Introduction ............................................................................................................................................ 60 Representation and Usage ...................................................................................................................... 60 Table Manipulation ................................................................................................................................. 62 Table Concatenation ............................................................................................................................... 62 Insert and Remove .................................................................................................................................. 63 Sorting Tables ......................................................................................................................................... 64 14. MODULES ............................................................................................................................ 66 What is a Module? .................................................................................................................................. 66 Specialty of Lua Modules ........................................................................................................................ 66 The require Function ............................................................................................................................... 67 Things to Remember ............................................................................................................................... 68 Old Way of Implementing Modules ........................................................................................................ 68 15. METATABLES ....................................................................................................................... 70 __index ................................................................................................................................................... 70 __newindex ............................................................................................................................................ 71 Adding Operator Behavior to Tables ....................................................................................................... 72 __call ...................................................................................................................................................... 74 __tostring ............................................................................................................................................... 75 16. COROUTINES ....................................................................................................................... 76 Introduction ............................................................................................................................................ 76 Functions Available in Coroutines ........................................................................................................... 76 What Does the Above Example Do? ........................................................................................................ 78 Another Coroutine Example .................................................................................................................... 78

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vi 17. FILE I/O................................................................................................................................ 81 Implicit File Descriptors .......................................................................................................................... 82 Explicit File Descriptors ........................................................................................................................... 83 18. ERROR HANDLING ............................................................................................................... 86 Need for Error Handling .......................................................................................................................... 86 Assert and Error Functions ...................................................................................................................... 87 pcall and xpcall ....................................................................................................................................... 88 19. DEBUGGING ........................................................................................................................ 90 Debugging – Example .............................................................................................................................. 93 Debugging Types ..................................................................................................................................... 94 Graphical Debugging ............................................................................................................................... 95 20. GARBAGE COLLECTION ....................................................................................................... 96 Garbage Collector Pause ......................................................................................................................... 96 Garbage Collector Step Multiplier ........................................................................................................... 96 Garbage Collector Functions ................................................................................................................... 96 21. OBJECT ORIENTED ............................................................................................................... 99 Introduction to OOP................................................................................................................................ 99 Features of OOP ...................................................................................................................................... 99 OOP in Lua .............................................................................................................................................. 99 A Real World Example........................................................................................................................... 100 Creating a Simple Class ......................................................................................................................... 100 Creating an Object ................................................................................................................................ 101 Accessing Properties ............................................................................................................................. 101 Accessing Member Function ................................................................................................................. 101 Complete Example ................................................................................................................................ 101

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vii Inheritance in Lua ................................................................................................................................. 102 Overriding Base Functions .................................................................................................................... 103 Inheritance Complete Example ............................................................................................................. 103 22. WEB PROGRAMMING ....................................................................................................... 106 Applications and Frameworks ............................................................................................................... 106 Orbit ..................................................................................................................................................... 106 Creating Forms ...................................................................................................................................... 109 WSAPI ................................................................................................................................................... 110 Xavante ................................................................................................................................................. 111 Lua Web Components ........................................................................................................................... 113 Ending Note .......................................................................................................................................... 113 23. DATABASE ACCESS ............................................................................................................ 115 MySQL db Setup ................................................................................................................................... 115 Importing MySQL .................................................................................................................................. 115 Setting up Connection ........................................................................................................................... 115 Execute Function................................................................................................................................... 116 Create Table Example ........................................................................................................................... 116 Insert Statement Example ..................................................................................................................... 117 Update Statement Example .................................................................................................................. 117 Delete Statement Example ................................................................................................................... 117 Select Statement Example .................................................................................................................... 117 A Complete Example ............................................................................................................................. 118 Performing Transactions ....................................................................................................................... 119 Start Transaction................................................................................................................................... 119 Rollback Transaction ............................................................................................................................. 119 Commit Transaction .............................................................................................................................. 119

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viii Importing SQLite ................................................................................................................................... 120 Setting Up Connection .......................................................................................................................... 120 Execute Function................................................................................................................................... 120 Create Table Example ........................................................................................................................... 120 Insert Statement Example ..................................................................................................................... 121 Select Statement Example .................................................................................................................... 121 A Complete Example ............................................................................................................................. 121 24. GAME PROGRAMING ........................................................................................................ 124 Corona SDK ........................................................................................................................................... 124 Gideros Mobile ..................................................................................................................................... 125 ShiVa3D ................................................................................................................................................ 125 Moai SDK .............................................................................................................................................. 126 LOVE ..................................................................................................................................................... 126 CryEngine .............................................................................................................................................. 126 An Ending Note ..................................................................................................................................... 127 25. STANDARD LIBRARIES ........................................................................................................ 128 Basic Library .......................................................................................................................................... 128 Modules Library .................................................................................................................................... 131 String manipulation .............................................................................................................................. 132 Table manipulation ............................................................................................................................... 132 File Input and output ............................................................................................................................ 132 Debug facilities ..................................................................................................................................... 132 26. MATH LIBRARY .................................................................................................................. 133 Trigonometric Functions ....................................................................................................................... 135 Other Common math Functions ............................................................................................................ 136

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ix 27. OPERATING SYSTEM FACILITIES......................................................................................... 138 Common OS functions .......................................................................................................................... 139

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Lua 1 Lua is an extensible, lightweight programming language written in C. It started as an in-house project in 1993 by Roberto Ierusalimschy, Luiz Henrique de Figueiredo, and Waldemar Celes. It was designed from the beginning to be a software that can be integrated with the code written in C and other conventional languages. This integration brings many benefits. It does not try to do what C can already do but aims at offering what C is not good at: a good distance from the hardware, dynamic structures, no redundancies, ease of testing and debugging. For this, Lua has a safe environment, automatic memory management, and good facilities for handling strings and other kinds of data with dynamic size. Features Lua provides a set of unique features that makes it distinct from other languages. These include:  Extensible  Simple  Efficient  Portable  Free and open Example Code print("Hello World!") How Lua is Implemented? Lua consists of two parts - the Lua interpreter part and the functioning software system. The functioning software system is an actual computer application that can interpret programs written in the Lua programming language. The Lua interpreter is written in ANSI C, hence it is highly portable and can run on a vast spectrum of devices from high-end network servers to small devices. Both Lua's language and its interpreter are mature, small, and fast. It has evolved from other programming languages and top software standards. Being small in size makes it possible for it to run on small devices with low memory. 1. OVERVIEW

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Lua 2 Learning Lua The most important point while learning Lua is to focus on the concepts without getting lost in its technical details. The purpose of learning a programming language is to become a better programmer; that is, to become more effective in designing and implementing new systems and at maintaining old ones. Some Uses of Lua  Game Programming  Scripting in Standalone Applications  Scripting in Web  Extensions and add-ons for databases like MySQL Proxy and MySQL WorkBench  Security systems like Intrusion Detection System.

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Lua 3 Try it Option Online We have already set up the Lua Programming environment online, so that you can build and execute all the available examples online at the same time when you are doing your theory work. This gives you confidence in what you are reading and to check the result with different options. Feel free to modify any example and execute it online. Try the following example using our online compiler option available at http://www.compileonline.com/ #!/usr/local/bin/lua print("Hello World!") For most of the examples given in this tutorial, you will find a Try it option in our website code sections at the top right corner that will take you to the online compiler. So, just make use of it and enjoy your learning. Local Environment Setup If you are still willing to set up your environment for Lua programming language, you need the following softwares available on your computer - (a) Text Editor, (b) The Lua Interpreter, and (c) Lua Compiler. Text Editor You need a text editor to type your program. Examples of a few editors include Windows Notepad, OS Edit command, Brief, Epsilon, EMACS, and vim or vi. Name and version of the text editor can vary on different operating systems. For example, Notepad will be used on Windows, and vim or vi can be used on Windows as well as Linux or UNIX. The files you create with your editor are called source files and these files contain the program source code. The source files for Lua programs are typically named with the extension ".lua". 2. ENVIRONMENT

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Lua 4 The Lua Interpreter It is just a small program that enables you to type Lua commands and have them executed immediately. It stops the execution of a Lua file in case it encounters an error unlike a compiler that executes fully. The Lua Compiler When we extend Lua to other languages/applications, we need a Software Development Kit with a compiler that is compatible with the Lua Application Program Interface. Installation on Windows There is a separate IDE named "SciTE" developed for the windows environment, which can be downloaded from http://code.google.com/p/luaforwindows/ download section. Run the downloaded executable to install the Lua IDE. Since it’s an IDE, you can both create and build the Lua code using the same. In case, you are interested in installing Lua in command line mode, you need to install MinGW or Cygwin and then compile and install Lua in windows. Installation on Linux To download and build Lua, use the following command: $ wget http://www.lua.org/ftp/lua-5.2.3.tar.gz $ tar zxf lua-5.2.3.tar.gz $ cd lua-5.2.3 $ make linux test In order to install on other platforms like aix, ansi, bsd, generic linux, mingw, posix, solaris by replacing Linux in make Linux, test with the corresponding platform name. We have a helloWorld.lua, in Lua as follows: print("Hello World!") Now, we can build and run a Lua file say helloWorld.lua, by switching to the folder containing the file using cd, and then using the following command: $ lua helloWorld

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Lua 5 We can see the following output. hello world Installation on Mac OS X To build/test Lua in the Mac OS X, use the following command: $ curl -R -O http://www.lua.org/ftp/lua-5.2.3.tar.gz $ tar zxf lua-5.2.3.tar.gz $ cd lua-5.2.3 $ make macosx test In certain cases, you may not have installed the Xcode and command line tools. In such cases, you won’t be able to use the make command. Install Xcode from mac app store. Then go to Preferences of Xcode, and then switch to Downloads and install the component named "Command Line Tools". Once the process is completed, make command will be available to you. It is not mandatory for you to execute the "make macosx test" statement. Even without executing this command, you can still use Lua in Mac OS X. We have a helloWorld.lua, in Lua, as follows: print("Hello World!") Now, we can build and run a Lua file say helloWorld.lua by switching to the folder containing the file using cd and then using the following command: $ lua helloWorld We can see the following output: hello world Lua IDE As mentioned earlier, for Windows SciTE, Lua IDE is the default IDE provided by the Lua creator team. The alternate IDE available is from ZeroBrane Studio, which is available across multiple platforms like Windows, Mac and Linux. There are also plugins for eclipse that enable the Lua development. Using IDE makes it easier for development with features like code completion and is highly recommended. The IDE also provides interactive mode programming similar to the command line version of Lua.

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Lua 6

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Lua 7 Let us start creating our first Lua program! First Lua Program Interactive Mode Programming Lua provides a mode called interactive mode. In this mode, you can type in instructions one after the other and get instant results. This can be invoked in the shell by using the lua -i or just the lua command. Once you type in this, press Enter and the interactive mode will be started as shown below. $ lua -i $ Lua 5.1.4 Copyright (C) 1994-2008 Lua.org, PUC-Rio quit to end; cd, dir and edit also available You can print something using the following statement: > print("test") Once you press enter, you will get the following output: 'test' Default Mode Programming Invoking the interpreter with a Lua file name parameter begins execution of the file and continues until the script is finished. When the script is finished, the interpreter is no longer active. Let us write a simple Lua program. All Lua files will have extension .lua. So put the following source code in a test.lua file. print("test") Assuming, lua environment is setup correctly, let’s run the program using the following code: $ lua test.lua 3. BASIC SYNTAX

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Lua 8 We will get the following output: test Let's try another way to execute a Lua program. Below is the modified test.lua file: #!/usr/local/bin/lua print("test") Here, we have assumed that you have Lua interpreter available in your /usr/local/bin directory. The first line is ignored by the interpreter, if it starts with # sign. Now, try to run this program as follows: $ chmod a+rx test.lua $./test.lua We will get the following output. test Let us now see the basic structure of Lua program, so that it will be easy for you to understand the basic building blocks of the Lua programming language. Tokens in Lua A Lua program consists of various tokens and a token is either a keyword, an identifier, a constant, a string literal, or a symbol. For example, the following Lua statement consists of three tokens: io.write("Hello world, from ",_VERSION,"!\n") The individual tokens are: io.write ( "Hello world, from ",_VERSION,"!\n" )

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Lua 9 Comments Comments are like helping text in your Lua program and they are ignored by the interpreter. They start with --[[ and terminates with the characters --]] as shown below: --[[ my first program in Lua --]] Identifiers A Lua identifier is a name used to identify a variable, function, or any other user-defined item. An identifier starts with a letter ‘A to Z’ or ‘a to z’ or an underscore ‘_’ followed by zero or more letters, underscores, and digits (0 to 9). Lua does not allow punctuation characters such as @, $, and % within identifiers. Lua is a case sensitive programming language. Thus Manpower and manpower are two different identifiers in Lua. Here are some examples of the acceptable identifiers: mohd zara abc move_name a_123 myname50 _temp j a23b9 retVal Keywords The following list shows few of the reserved words in Lua. These reserved words may not be used as constants or variables or any other identifier names. and break do else elseif end false for function if in local nil not or repeat return then true until while

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Lua 10 Whitespace in Lua A line containing only whitespace, possibly with a comment, is known as a blank line, and a Lua interpreter totally ignores it. Whitespace is the term used in Lua to describe blanks, tabs, newline characters and comments. Whitespace separates one part of a statement from another and enables the interpreter to identify where one element in a statement, such as int ends, and the next element begins. Therefore, in the following statement: local age There must be at least one whitespace character (usually a space) between local and age for the interpreter to be able to distinguish them. On the other hand, in the following statement: fruit = apples + oranges --get the total fruit No whitespace characters are necessary between fruit and =, or between = and apples, although you are free to include some if you wish for readability purpose.