Lua Programming Directory, Links. Development, Programmers, Programmer Reference, Resources @ eIT.in

Add Links: If you have a web site that you wish to include in this database, do let us know the details by sending a note about your URL to narsi@esource.in. We’ll quickly review the web site, and if found relevant, add it to the database. We look forward to web site owners and link exchange partners to submit URL. Thanks!

Looking for an outsourcing partner for software programming & development? Have you talked to us?

Other IT Web Sites from eIT.in

Content derived from Wikipedia article on Lua Programming Language

Lua (programming language)

From Wikipedia, the free encyclopedia

Lua

Paradigm: Multi-paradigm

Appeared in: 1993

Waldemar Celes

Luiz Henrique de Figueiredo

Latest release: 5.1.1 / June 9th, 2006

Influenced by: Scheme, Icon

Influenced: Io

OS: Cross-platform

License: MIT License

Website: www.lua.org

In computing, the Lua (pronounced LOO-ah, or /'lua/ in IPA) programming language is a lightweight, reflective, imperative and procedural language, designed as a scripting language with extensible semantics as a primary goal. The name is derived from the Portuguese word for moon.

Contents

1 Philosophy

2 History

3 Features

3.1 Example code

3.2 Tables

3.2.1 Table as structure

3.2.2 Table as array

3.3 Object-oriented programming

4 Internals

5 Applications

5.1 Games

5.2 Other applications

6 Books

7 External links

Philosophy

Lua is commonly described as a "multi-paradigm" language, providing a small set of general features that can be extended to fit different problem types, rather than providing a more complex and rigid specification to match a single paradigm. Lua, for instance, does not contain explicit support for inheritance, but allows it to be implemented relatively easily with metatables. Similarly, Lua allows programmers to implement namespaces, classes, and other related features using its single table implementation; first class functions allow the employment of many powerful techniques from functional programming; and full lexical scoping allows fine-grained information hiding to enforce the principle of least privilege.

In general, Lua strives to provide flexible meta-features that can be extended as needed, rather than supply a feature-set specific to one programming paradigm. As a result, the base language is light—in fact, the full reference interpreter is only about 150KB compiled—and easily adaptable to a broad range of applications.

History

Lua was created in 1993 by Roberto Ierusalimschy, Luiz Henrique de Figueiredo, and Waldemar Celes, members of the Computer Graphics Technology Group at PUC-Rio, the Pontifical University of Rio de Janeiro, in Brazil. Versions of Lua prior to version 5.0 were released under a license similar to the BSD license. From version 5.0 onwards, Lua has been licensed under the MIT License.

Lua has been used in many commercial applications, such as Far Cry, World of Warcraft and Adobe Photoshop Lightroom, as well as non-commercial applications, such as Angband and its variants. (See the Applications section for a more detailed list.) A ported version of Lua has been used to program homebrew for the Playstation Portable and then Nintendo DS.

Some of its closest relatives include Icon for its design and Python for its ease of use by non-programmers. In a paper published in Dr. Dobb's Journal, Lua's creators also state that LISP and Scheme with their single, ubiquitous data structure mechanism (the list) were a major influence on their decision to develop the table as the primary data structure of Lua.[1]

Features

Lua is a dynamically typed language intended for use as an extension or scripting language, and is compact enough to fit on a variety of host platforms. It supports only a small number of atomic data structures such as boolean values, numbers (double-precision floating point by default), and strings. Typical data structures such as arrays, sets, hash tables, lists, and records can be represented using Lua's single native data structure, the table, which is essentially a heterogeneous map.

Lua has no built-in support for namespaces and object-oriented programming. Instead, metatable and metamethods are used to extend the language to support both programing paradigms in an elegant and straight-forward manner.

Lua implements a small set of advanced features such as higher-order functions, garbage collection, first-class functions, closures, proper tail calls, coercion (automatic conversion between string and number values at run time), coroutines (collaborative multithreading) and dynamic module loading.

By including only a minimum set of data types, Lua attempts to strike a balance between power and size.

Example code

The classic hello world program can be written as follows:

print "Hello, world!"

The factorial is an example of a recursive function:

function factorial(n)

if n == 0 then

return 1

end

return n * factorial(n - 1)

end

Lua's treatment of functions as first class variables is shown in the following example, where the print function's behavior is modified:

local oldprint = print -- store current print function as old print

print = function(s) -- redefine print function

if s == "foo" then

oldprint("bar")

else

oldprint(s)

end

Any future calls to "print" will now be routed through the new function, and thanks to Lua's lexical scoping, the old print function will only be accessible by the new, modified print.

Extensible semantics is a key feature of Lua, and the "metatable" concept allows Lua's tables to be customized in powerful and unique ways. The following example demonstrates an "infinite" table. For any n, fibs[n] will give the nth Fibonacci number using dynamic programming.

fibs = { 1, 1 } -- Initial values for fibs[1] and fibs[2].

setmetatable(fibs, { -- Give fibs some magic behavior.

__index = function(fibs,n) -- Call this function if fibs[n] does not exist.

fibs[n] = fibs[n-2] + fibs[n-1] -- Calculate and memoize fibs[n].

return fibs[n]

end

})

Tables

Tables are the most important data structure in Lua, and are the foundation of all user-created types.

The table is a collection of key and data pairs (known also as hashed heterogeneous associative array), where the data is referenced by key. The key (index) can be of any data type except nil.

Table as structure

Tables are often used as structures (or objects) by using strings as keys. Because such use is very common, Lua features a special syntax for accessing such fields. Example:

point = { x = 10, y = 20 } -- Create new table

print( point["x"] ) -- Prints 10

print( point.x ) -- Has exactly the same meaning as line above

Table as array

By using a numerical key, the table resembles an array data type.

A simple array of the strings:

array = { "a", "b", "c", "d" } -- Indexes are assigned automatically

print( array[2] ) -- Prints "b"

An array of objects:

function Point(x,y) -- "Point" object constructor

return {x = x, y = y} -- Creates and returns a new object (table)

end

array = { Point(10,20), Point(30,40), Point(50,60) } -- Creates array of points

print( array[2].y ) -- Prints 40

Object-oriented programming

Although Lua does not have a built-in concept of classes and objects, the language is powerful enough to easily implement them using two language features: first-class functions and tables. By simply placing functions and related data into a table, an object is formed. Inheritance (both single and multiple) can be implemented via the "metatable" mechanism, telling the object to lookup nonexistent methods and field in parent object(s).

There is no such concept as "class" with these techniques, rather "prototypes" are used as in Self programming language. New objects are created either with a factory method (that constructs new objects from scratch) or by cloning an extant object.

Internals

Lua programs are not interpreted directly, but are compiled to bytecode which is then run on the Lua virtual machine. The compilation process is typically transparent to the user and is performed during run-time, but it can be done offline in order to increase performance or reduce the memory footprint of the host environment by leaving out the compiler.

There is also a third-party just-in-time Lua run-time, called LuaJIT, for the new 5.1 version.

This example is the bytecode listing of the factorial function described above (in Lua 5.0):

function <factorial.lua:1> (10 instructions, 40 bytes at 00326DA0)

1 param, 3 stacks, 0 upvalues, 1 local, 3 constants, 0 functions

1 [2] EQ 0 0 250 ; compare value to 0

2 [2] JMP 0 2 ; to line 5

3 [3] LOADK 1 1 ; 1

4 [3] RETURN 1 2 0

5 [6] GETGLOBAL 1 2 ; fact

6 [6] SUB 2 0 251 ; - 1

7 [6] CALL 1 2 2

8 [6] MUL 1 0 1

9 [6] RETURN 1 2 0

10 [7] RETURN 0 1 0

Applications

Lua, as a compiled binary, is very small by code standards. Coupled with its relatively fast speed, and its very lenient license, it has gained a following among game developers for providing a viable scripting interface.

Games

LucasArts GrimE engine for adventure games, first released on 1998, uses Lua internally.

Grim Fandango was the first game based on this engine.

Escape From Monkey Island was the first in the Monkey Island series to switch to the Lua language.

World of Warcraft, a fantasy MMORPG. Lua is used to allow users to customize its user interface, character animation and world appearance.

Far Cry, a first-person shooter. Lua is used to script a substantial chunk of the game logic, manage game objects (Entity system), configure the HUD and store other configuration information.

Bioware's Baldur's Gate series

Relic Entertainment's Company of Heroes, Warhammer 40000 Dawn of War, Homeworld 2 and Impossible Creatures all use Lua.

Mercenaries: Playground of Destruction for Playstation 2 has good-sized chunks of Lua in it.

Garry's Mod, a Half-Life 2 mod. Lua is used to script things such as custom game modes, weapons, HUDs, and more.

Vendetta Online, a space massively multiplayer online role-playing game

MDK2, uses Lua as a module scripting language.

Supreme Commander, uses Lua

TASpring, uses Lua

Ragnarok Online recently had a Lua implementation, allowing players to fully customize the artificial intelligence of their homunculus to their liking, provided that they have an Alchemist to summon one.

Nival Interactive's Heroes of Might and Magic V and Silent Storm

Bully

Sonic the Hedgehog (2006), uses Lua

StepMania uses Lua

Other applications

Therescript, used to drive the vehicles and animations in There, is Lua plus some application-specific functions.

The window manager Ion uses Lua for customization and extensibility.

The packet sniffer Wireshark uses Lua for scripting and prototyping.

The Aegisub subtitles manipulation program uses Lua in its automation module, to generate advanced effects, such as karaoke.

RM-X General Purpose Control exposes a Lua interface to plugins that can either extend scripts by providing functions or call scripts dynamically at runtime.

Intellipool Network Monitor uses Lua for customization and extensibility.

In the Klango Environment, Lua is used as a programming language for developing audio games and applications, a software dedicated to the blind and visually impaired. (external link)

Lua Player is a port designed to run on Sony Computer Entertainment's PlayStation Portable to allow entry-level programming.

Adobe Lightroom, a beta digital photography post-production program, contains a large amount (40%) of Lua code.

FreePOPs, a program designed for checking and retrieving webmail through a conventional POP3 program.

ELinks, a web browser

TomsRtBt, a single-floppy Linux Rescue disk has most of the userland applications re-written in Lua

A list of projects known to use Lua is located at Lua.org.

Books

Programming in Lua, Second Edition (ISBN 85-903798-2-5)

Game Development with Lua (ISBN 1-58450-404-8)

External links

Lua.org

Lua mailing list

Lua-users wiki

VSLua Complete Visual Studio (2002, 2003, 2005) integrated editor and optimized embedded debugger for Lua.

LuaForge hosting for, and a catalog of, Lua projects.

LuaEdit complete professional looking IDE for Lua - Windows 98/2000/XP

LuaJIT just-in-time compiler

LuaBind to bind functions and classes from C++ to Lua code.

Plua is a port of Lua 4.0 (plus a small IDE) for the Palm Computing platform; see Plua.

Kepler Project Web Development Platform for Lua.

murgaLua GUI, Network, Database and XML Application Development Platform for Lua.

onlamp.com: Introducing Lua

Lua Tutorials How to embed & extend Lua in C / C++

Retrieved from http://en.wikipedia.org/wiki/Lua_%28programming_language%29

End of Wikipedia content, http://en.wikipedia.org/wiki/Lua_programming_language

Web Resources for Lua Programming Language

More eIT.in References

o Programming Languages

§ The A-Z of Programming Languages

§ A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z

§ L

· LabVIEW

· Lava

· Limbo

· Lisp

· Lingo

· Logo

· Lua

Main Sections @ eIT.in

Software

· Free & Open Source Software

· Operating Systems

o Mainframe & Legacy Operating Systems

· Midrange

· Mainframe Operating Systems

· Databases

· Programming & Development Directory

o Programming Languages

§ The A-Z of Programming Languages

§ A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z

· Internet & Web

§ Web Servers

§ Application Servers

§ Server Side Scripting

§ Web Services

Computer Hardware
Networking & Communications Technologies
IT Strategy & Design
IT in Industries & Businesses
IT in Functions & Business Processes

IT Infrastructure
Tech Support
IT, Software Industry, Trade & Business Network
IT, Software Industry News & Updates

About eIT.in

eIT.in is a comprehensive directory for everything IT & Software. It contains over 500 categories, and well over 10,000 web resources

eIT.in provides directory and web links resources for the IT, software, programming & software development domains. It is intended to be useful for application, applications programmers & developers, software technology programmer & developer, databases software development, administrators & DBAs, application developers, strategy architect, design specialists and architects, migration, integration, customization consultants and customisation analysts, administration, maintenance & support professionals, outsourcing consultant, bespoke solutions programming developers & coders, project management & functional analyst, and for system administrators, testing & quality control engineers. It will make an effort to provide resources on tutorial/tutorials, guide, guides, tips, faq, faqs on these topics.

eIT.in content is available under GPL: All directory content at mainframe.in is under the General Public License (GPL). Under this license, anyone is free to copy & use any amount of directory content @ eIT.in, make changes to it and use it in any way they wish, as long as they also allow the same rights to anyone else for this content. The concept of GPL has been adapted from the GNU GPL of the Free Software Movement. To those who wish to use content from eIT.in, our only request is that they acknowledge the source and provide a link back to eIT.in. This is only a request!

Countries & Cities Where eIT.in Provides Assistance

eIT Cities: Bangalore, Chennai, Mumbai, Bhubaneswar, Mysore, Kolkaka, Delhi, Pune, Trivandrum, Hyderabad

United States of America - Alabama (AL) - Birmingham, Huntsville, Mobile, Montgomery, Arkansas (AR) - Little Rock, Arizona (AZ) - Phoenix, Tucson, California (CA) - Bakersfield, Fresno, Los Angeles, Modesto, Oakland, Orange Country, Riverside, Sacramento, Salinas, San Diego, San Francisco, San Jose, Santa Barbara, Santa Rosa, Stockton, Vallejo, Ventura, Visalia, Colorado (CO) - Colorado Springs, Denver, Connecticut (CT) - Hartford, Southern Connecticut (Southern Conn), Delaware (DE) – Wilmington, Florida (FL) - Daytona Beach, Fort Lauderdale, Fort Myers, Fort Pierce, Jacksonville, Lakeland, Melbourne, Miami, Orlando, Pensacola, Sarasota, Tampa, West Palm Beach, Georgia (GA) - Atlanta, Augusta, Hawaii (HI) – Honolulu, Iowa (IA) - Davenport, Des Moines, Idaho (ID) – Boise, Illinois (IL) - Chicago, Peoria, Rockford, Indiana (IN) - Fort Wayne, Gary, Indianapolis, Kansas (KS) – Wichita, Kentucky (KY) - Lexington, Louisville, Louisiana (LA) - Baton Rouge, Lafayette, New Orleans, Shreveport, Massachusetts (MA) - Boston, Springfield, Maryland (MD) – Baltimore, Michigan (MI) - Ann Arbor, Detroit, Flint, Grand Rapids, Kalamazoo, Lansing, Saginaw, Minnesota (MN) - Minneapolis – St. Paul, Missouri (MO) - Kansas City, St. Louis, Mississippi (MS) - Biloxi, Jackson, North Carolina (NC) - Charlotte, Greensboro, Hickory, Raleigh-Durham, Nebraska (NE) – Omaha, New Jersey (NJ) - Atlantic City, Bergen-Passaic, Jersey City, Mercer, Middlesex, Monmouth, Newark, New Mexico (NM) – Albuquerque, Nevada (NV) - Las Vegas, Reno, New York (NY) - Albany, Buffalo, Nassau-Suffolk, New York, Orange County, Rochester, Syracuse, Ohio (OH) - Akron, Canton, Cincinnati, Cleveland, Columbus, Dayton, Hamilton, Toledo, Youngstown, Oklahoma (OK) - Oklahoma City, Tulsa, Oregon (OR) - Portland, Salem, Pennsylvania (PA) - Allentown, Harrisburg, Lancaster, Philadelphia, Pittsburgh, Reading, Scranton, York, Rhode Island (RI) – Providence, South Carolina (SC) - Charleston, Columbia, Greenville, Tennessee (TN) - Chattanooga, Johnson City, Knoxville, Memphis, Nashville, Texas (TX) - Austin, Beaumont, Brownsville, Corpus Christi, Dallas, El Paso, Fort Worth, Houston, McAllen, San Antonio, Utah (UT) - Provo, Salt Lake City, Virginia (VA) - Norfolk, Richmond, Washington (WA) - Seattle, Spokane, Tacoma, Wisconsin (WI) - Appleton, Madison, Milwaukee, District of Columbia (DC) - Washington, DC

Canada

Provinces - Alberta > Cities: Calgary, Edmonton; British Columbia > Cities: Victoria, Vancouver; Prince Edward Island; Manitoba > Cities: Winnipeg; New Brunswick; Nova Scotia > Cities: Halifax; Nunavut > Cities: Iqaluit; Ontario > Cities: Toronto, Ottawa, Hamilton, London, Kitchener, St. Catharines-Niagara, Windsor; Quebec > Cities: Quebec City, Montreal; Saskatchewan > Cities: Saskatoon, Regina

Territories - Newfoundland and Labrador; Northwest Territories; Yukon Territory

Australia – Sydney, Melbourne, Brisbane, Perth, Adelaide, Newcastle, Gold Coast, Canberra, Wollongong, Sunshine Coast, Hobart, Geelong, Townsville, Cairns, Launceston

Europe - Luxembourg - Luxembourg City, Belgium – Brussels (Brussel), Antwerp (Antwerpen), Ghent (Gent, Gand), Charleroi, Liège (Liege), Austria - Vienna (Wien), Graz, Linz, Salzburg, Innsbruck, Netherlands - Amsterdam, Rotterdam, Utrecht, Eindhoven, Tilburg, ‘s-Gravenhage (sGravenhage), Groningen, France - Paris, Marseille, Lyon, Toulouse, Nice, Nantes, Strasbourg, Montpellier, Bordeaux, Germany - Berlin, Hamburg, Munich (München), Cologne (Köln), Frankfurt (Frankfurt am Main), Essen, Dortmund, Stuttgart, Düsseldorf, Bremen, Duisburg, Hannover, Nürnberg (Nuremberg), Dresden, Leipzig, Norway - Oslo, Bergen, Stavanger, Trondheim, Denmark – Copenhagen (Københavns), Aarhus (Århus), Odense, Aalborg (Ålborg), Sweden - Stockholm, Goteborg (Göteborg), Malmo (Malmö), Uppsala, Vasteras (Västerås), Finland – Helsinki (Helsingin), Espoo, Tampere (Tampereen), Vantaa, Turku, Oulu, Spain - Madrid, Barcelona, Valencia, Sevilla, Zaragoza, Malaga, Murcia, Las Palmas, Bilbao, Switzerland – Zürich (Zurich), Geneva (Geneve, Genève), Basel, Bern (Berne), Lausanne, UK - London, Birmingham, Glasgow, Liverpool, Sheffield, Leeds, Bristol, Manchester, Edinburgh, Leicester, Italy - Rome (Roma), Milan (Milano), Napoli (Naples), Torino (Turin), Palermo, Bologna, Firenze (Florence), Genova (Genoa)

eIT.in is a product of eSource India & Sourcing India

Other eSource & Sourcing sites: IT & Software (Dir, SAP), BPO, Chemicals, Textiles, Plant Oils, dotMobi, Billion Dollar Questions,

Biodiesel Encyclopedia, Linens, ideOS, Follars – Free, Open-source Dollars, Quali5.com – Own A Keyword Forever, AntiSE, Serkai, Leather & Hide, GeoDig