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Beginning Lua Programming

samzenpus posted more than 7 years ago | from the get-started dept.

Book Reviews 173

Simon P. Chappell writes "These days, Brazil is no longer just on the map for its fine coffee and martial arts. They have a few other reasons and one of them is called Lua. Lua is an open-source scripting language that was originally designed for small size and excellent portability to support its use in embedded systems. Like anything good, it didn't take long for it to be discovered by others looking for a small and efficient scripting language."

This is definitely a book targeted at those new to Lua. While it begins gently, it picks up speed quite quickly and takes its reader through a full range of Lua usage. This book is unusual, for the more mass-market beginner books, in that it does not treat the reader like an idiot. I found the tone to be very respectful of the reader's intelligence. This aspect alone, makes the book stand out in a crowded beginners market.

This book is also a very good introduction to Lua for programmers experienced with one or more other programming languages. I found it very easy to pick up the concepts with my previous programming experience.

The first chapter of most books like this, will typically cover getting setup with the language. This book delivers well, with not only explaining how to install the binary version, but also covers compilation under Unix-styled operating systems and a number of development environments for Microsoft Windows. Guidelines are given for building Lua on Windows using Visual C++, Tiny C and MinGW.

Chapter two is called "First Steps" and is a walkthrough of all of the core language. This is well done and there are plenty of examples where a Lua command is typed and the resulting display from the Lua environment is shown. Chapter three is dedicated to the art of the Lua function. Functions are first class values and have enough power and complexity that they deserve their own chapter. Did you know that Lua automatically recognises tail recursion and handles it appropriately? It does. So if your looking to experiment with some of the trendy functional techniques that tend to swamp Reddit these days, Lua would be a good place to try it.

Chapter four explores Lua's only data structure, the table. What's a table, you ask? My best description, as far as I've managed to get my head around it, would be that it's a Swiss-Army Knife style Hash Table with multiple personalities, alternatively thinking that it's an array, a list, an Erlang-style tuple or a tree structure. However you decide to use it, this chapter explains it and provides lots of examples. Chapter five brings us that ultimate datatype, the string. As with tables, Lua can do many things with the humble string and this chapter will make sure that you can work with substrings, handle user input, read and write files and use the built-in pattern matching available in the language.

Chapter six covers "Handling and Avoiding Errors". I know, I know, we don't have errors anymore, now that we've all discovered the benefits of agile development using scripting languages. Except that we do and circumstances external to our programs can still bring pain to our code. Users type the wrong things, network connections die, power can go out suddenly and, of course, sometimes there are parts of our programs that aren't as imperfect as we'd like to think they are. Chapter seven is about "Using Modules" and explains Lua's interfaces and implementations together with guidelines on modularising scripts and calling those modules.

Any agile language worth its electrons is going to have meta-programming facilities within it. Lua has them and chapter eight is where we learn about "Extending Lua's Behaviour with Metamethods". Chapter nine examines Lua's ability to handle events using coroutines. This is a powerful feature and enables Lua applications to manage concurrent tasks with ease.

Chapter ten explores the fascinating world of Lua internals. While Lua is a scripting language, it does use a virtual machine, this chapter shows how scripts can be pre-compiled to the appropriate bytecode. It also covers memory management and implementation details for tables and strings. Chapter eleven is somewhat reference-like, covering the standard libraries supplied with Lua. Chapter twelve is a good compliment, describing some of the available libraries from the Lua community.

Chapter thirteen addresses the matter of interfacing Lua with other languages. If your language can handle C-style calling conventions, then it can be used by your Lua programs. Chapter fourteen is for everyone that wishes to store information in a database now and then. Lua has bindings for connecting to a number of popular database systems and this chapter will help you use them.

My favourite chapter is number fifteen, where using Lua for web applications is explained. There are several alternatives for the budding Lua web application programmer, ranging from that humble and faithful technique, the CGI script, to the Kepler web server environment with the convenience of LuaPages. In this highly-connected world, it is important to be able to communicate over a network and if chapter fifteen didn't tip you off, then chapter sixteen will make you absolutely certain that Lua is ready for networks. Chapter sixteen explores networking from LuaSockets to email and webpages.

Lua is very popular among video games designers. While not generally used to write the frameworks, it is often used for in-game scripting. Chapter seventeen recounts many of the ways that Lua can be used within video games. Chapter eighteen will appeal to the Palm carrying geeks in the house. If you've been looking for a programming language for your Palm PDA, then Plua may be just what you were looking for. Plua (actually Plua2, but they call it Plua) is an implementation of Lua 5.0 for the Palm OS. It gives full access to both data and graphics and is programmable on the Palm; no need to be tethered. Finally, chapter nineteen addresses the subject of "Fitting into the Lua Community".

That's a long list of chapters. Phew! After all of that, let's see what was worth noting along the way.

The writing style is good. Light without being flippant and respectful of the readers intelligence. I like that. I liked the fact that the topics were broken down into appropriately sized chapters. It meant that this book has more chapters than usual, but each one is nicely partitioned, so it doesn't feel over-whelming. I also like the fact that this book seems like it will continue to be useful in the medium term as well. Some beginners books stop being useful quite quickly after you've learned the basics from them, but this one covers quite a number of topics that will useful at the mid-level of Lua skills.

I have very little negative to say about the book. While I normally don't care for books much larger than 300 pages, this one doesn't feel like it has any gratuitous stuffing in it. There is an appendix with answers to the programming questions asked here and there in the chapters, but other than that, everything feels like it should be there.

As a typography and layout nut, I did feel that the layout was a little cramped and the primary type size was a little small. The program listings were generally well done, although I'm not sure that every single one needed a gray background to help separate it from the body text.

The title of chapter nineteen, "Fitting into the Lua Community" seemed a little patronizing to me. I understand the need for maintaining community values, but most communities do that fairly well without the aid of authors playing the heavy. Apparently the community lasted this long without the book. Let's hope they make it a little longer, now that the masses know about it.

All in all, this is a great introduction to Lua. It has solid writing and explanations of the concepts, with plenty of examples. Recommended.


You can purchase Beginning Lua Programming from amazon.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.

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173 comments

LUA in WoW (5, Informative)

Anonymous Coward | more than 7 years ago | (#18577529)

Blizzard uses LUA as the scripting language for macros and UI controls in the World of Warcraft MMORPG.

Re:LUA in WoW (1)

moochfish (822730) | more than 7 years ago | (#18579991)

Not trying to troll, but in all honesty with tons of other proven languages out there, why did blizzard bank on this one? what makes this language so great? i read the wiki article, but it seems like this is a relative new comer with very limited documented use in the production world (no pun intended), let alone a scaling application like WoW. Does anybody know?

Yeah... (2, Funny)

phasm42 (588479) | more than 7 years ago | (#18577539)

These days, Brazil is no longer just on the map for it's fine coffee and martial arts.
I pretty much stopped reading after that.

Re:Yeah... (1, Troll)

syphax (189065) | more than 7 years ago | (#18577597)


That struck me as odd, too. A joke? I always thought Brazil was on the map for the Amazon, Carnaval, and fine women (see: Carnaval). I suppose you can also add ethanol and insane gang and prison violence.

Insane gang and prision violence?? (1, Insightful)

Anonymous Coward | more than 7 years ago | (#18577789)

You mean just like the US of A??

Re:Insane gang and prision violence?? (0)

Anonymous Coward | more than 7 years ago | (#18578855)

Score:5, Tu Quoque

Re:Yeah... (0, Troll)

garcia (6573) | more than 7 years ago | (#18577861)

I always thought Brazil was on the map for the Amazon, Carnaval, and fine women (see: Carnaval). I suppose you can also add ethanol and insane gang and prison violence.

You forgot hacking.

Re:Yeah... (1)

syphax (189065) | more than 7 years ago | (#18577911)

... and soccer/football. And free culture (eg Minister of Culture Gilberto Gil [wikipedia.org] )

Re:Yeah... (3, Funny)

Threni (635302) | more than 7 years ago | (#18577651)

>>These days, Brazil is no longer just on the map for it's fine coffee and martial arts.

>I pretty much stopped reading after that.

Exactly. If theres one thing I cant s'tand its people who dont know how to us'e punctuation.

Re:Yeah... (4, Funny)

Eccles (932) | more than 7 years ago | (#18577655)

I was thinking of a particular, uh, "haircut" myself...

Re:Yeah... (1)

Knux (990961) | more than 7 years ago | (#18578739)

These days, Brazil is no longer just on the map for it's fine coffee and martial arts.

There's also corruption, prostitution...

Re:Yeah... (1)

jesterman (932975) | more than 7 years ago | (#18579831)

There's also corruption, prostitution...

Thank god no such things exist in rest of the world! Oh my, Brazil is soo 'retro'...

Re:Yeah... (1)

drooling-dog (189103) | more than 7 years ago | (#18579045)

I was going to add "bathing suits, bikini wax, and babes" but it looks like my esteemed colleagues here have beaten me to it...

Re:Yeah... (1)

yoyoq (1056216) | more than 7 years ago | (#18579733)

i stopped reading after "These days"

Lua's not new (0)

Anonymous Coward | more than 7 years ago | (#18580025)

And what's with the "it didn't take long" nonsense? Lua isn't exactly new ya know.

WoW (2, Informative)

dsraistlin (901406) | more than 7 years ago | (#18577547)

It is also the scripting language that is used for WoW mods.

LUA in games (2, Informative)

mkithara (589429) | more than 7 years ago | (#18578079)

It's also the scripting language used by Supreme Commander.

Re:LUA in games (1, Informative)

Anonymous Coward | more than 7 years ago | (#18578535)

It is also is heavily used in Adobe Lightroom [poundbang.in] .

When asked how to get ready for the upcoming Lightroom SDK, an Adobe engineer said "Go hack WoW and come back when we have the SDK ready."

Re:LUA in games (2, Interesting)

koxkoxkox (879667) | more than 7 years ago | (#18579585)

Lua is not only used in games.

As another example of what you can do with Lua, it is used in Ion, a window manager (http://modeemi.fi/~tuomov/ion/ [modeemi.fi] ). Granted, it is a little known window manager, intended for people who dislike mouse and fancy graphic effects, but it has been designed to be a lightweight solution and that's why Lua had been chosen.

http://www.yzis.org/ [yzis.org] uses it also.

Another scripting language? (1)

spike2131 (468840) | more than 7 years ago | (#18577579)

What advantage does Lua have over perl/python/ruby/other existing scripting languages that makes it worth investing the time to learn?

Re:Another scripting language? (4, Informative)

Anonymous Coward | more than 7 years ago | (#18577707)

It's very lightweight and used in fields where a full language is needed but the overhead of a Perl/Python/Ruby is unacceptable. Plus the 'sole' datatype is pretty flexible (can be used to code OO (prototypical & definition), Modules, namespaces &c.). It's also pretty damn fast, and quite solid for general use. The wikipedia entry has a decent list of games & apps that it's being used in.

I must agree though that this article didn't do too much in terms of selling the language, which is probably what the book is supposed to do.

Re:Another scripting language? (4, Insightful)

Jimmy_B (129296) | more than 7 years ago | (#18577745)

What advantage does Lua have over perl/python/ruby/other existing scripting languages that makes it worth investing the time to learn?

Lua is useful because it's easy to fold into other programs. Lua is what you pull out when you're writing an application in a non-scripting language but you decide to make part of it user-scriptable. Conversely, you may be using one of those applications, in which case there are Lua scripts around for you to play with.

Some examples of what it's good for (4, Informative)

Anonymous Coward | more than 7 years ago | (#18579161)

Lua's C API is rather stellar. It makes it very easy to jump between Lua and C code near-infinitely, to access C functions from Lua and Lua functions from C, often nested multiple times that way.

It's also extremely small in terms of memory size and footprint, making it ideal for some embedded applications. I've used it to create a (yes, really) AJAX-enabled web-UI for configuring small Linux boards.

I had to write some sqlite bindings for Lua to do it (sorry, closed source, GRRR) but it really wasn't even remotely hard.

On the downside, most Lua projects start to feel like Lisp as you start to add your own language support for things that aren't in the core, and it's best to avoid the object/module support -- that's rather hairy stuff.

Re:Another scripting language? (1)

scorpionsoft (590852) | more than 7 years ago | (#18577763)

IIRC, Lua is the scripting language used for World of Warcraft user interface modifications. A decent practical reason, at least!

Re:Another scripting language? (2, Informative)

Anonymous Coward | more than 7 years ago | (#18577813)

It's also used to configure damn near everything in Homeworld 2. You can tweak anything with just notepad.

when they say "lightweight"... they mean it (5, Informative)

FooAtWFU (699187) | more than 7 years ago | (#18577849)

You use Lua for your in-game scripting of your computer games. Can you fit your Perl/Python/Ruby interpreter in 150 kilobytes? I didn't think so. Can you get it under a MIT license? I don't think you can.

Should you use it for your online web application backend, or your system administration scripts? Probably not.

Re:when they say "lightweight"... they mean it (2, Insightful)

winkydink (650484) | more than 7 years ago | (#18577971)

I believe I can get perl under the Artistic License. How does the MIT license differ in a way that is advantageous?

Re:when they say "lightweight"... they mean it (1)

SanityInAnarchy (655584) | more than 7 years ago | (#18579929)

Can you fit your Perl/Python/Ruby interpreter in 150 kilobytes?

Does it matter?

Here, let me fix this for you:

You use Lua for your in-game scripting of your computer games which are written in statically-compiled languages.

If the game had been written in Perl/Python/Ruby in the first place, no additional scripting language would be needed. Granted, Python is probably the only one of those that's reasonably fast enough, but still...

It is extremely easy to embed. (4, Insightful)

pavon (30274) | more than 7 years ago | (#18577913)

If you want to add scripting functionality to an existing application Lua is by far the easiest way to do so, and it has an added benifit being more efficient (both in terms of memory consumption and execution speed) than python or ruby. It is fairly easy for power-users to learn, as it is simular to javascript in many ways, and yet is also powerfull, as it is a complete functional language. For these reasons, you are seeing it being used more and more in open source desktop applications as well as many big name games such as WoW.

I don't know that I would go out of my way to learning it just to learn it, but I would love to see it become the defacto scripting language for linux desktop apps.

YAML versus XML or JSON (1)

goombah99 (560566) | more than 7 years ago | (#18578011)

Asking what Lua has over Perl/python is like asking what YAML has over XML. You can do more in XML but it's not a lightweight format. YAML is clean and human readable, and fast to parse. It's so lightweight that I actually use it in my Python program to define complex structures of constants, since it's actually a cleaner syntax than the python code itself!

Indeed there are extremely few XML applications I have seen that would not be much better served by YAML. for example, .plist files on macs ought to be YAML. this would make a much better bridge between unix flat file configs and the desired database style configs that .plist achieve. (On the other hand things like markup languages for complex text layout are apropos for XML. my point is very few places benefit from XML.)

So the analogy here is that sometimes simpler is more useful than full featured. the trick is getting the most out of the least, not simply removing features from the complex form. Besides which To the extent that YAML is turing complete it's as good as anything else. Just as YAML can in principle represent anything that XML can.

Re:YAML versus XML or JSON (1)

billcopc (196330) | more than 7 years ago | (#18578335)

Finally someone with a brain! I thought I was the only guy who sees XML for the bloated non-solution that it is! Of course, the internets love acronyms (see AJAX). Personally, I prefer fast and lean binary encoding (with complete documentation of its structures) but all these late generation programmers are allergic to anything that existed before 1998 :P

Re:YAML versus XML or JSON (0)

Anonymous Coward | more than 7 years ago | (#18578671)

No, you're kinda late to the party. Pretty much everybody who isn't a Java weenie has given up on XML and the overly-complex formats/specs that surround it except in the places where it's already thoroughly entrenched (we're kind of stuck with RSS and Atom, for example).

Re:YAML versus XML or JSON (1)

TuringTest (533084) | more than 7 years ago | (#18580101)

I prefer fast and lean binary encoding (with complete documentation of its structures)

You put that in parentheses as a secondary characteristic, but that's the very distinguishing reason why XML was invented. You're not supposed to need complete documentation for using a XML file format, they should mostly self-documenting - it was designed as a flexible format for interchange. Binary and XML are for different goals, you preferring one over the other is like saying that you prefer cars over railways because they're oh so easier to park in your garage.

Problem is not that XML is bloated, is that it's being used for something it was not intended. But thanks to its desirable property of having universal parsers now it's being used elsewhere. Before 1998 you'd have to build your own parsers for every file format using yacc or bison, today you can reuse code - even when it's not be the best solution. But you can't blame programmers for following the path of least resistance.

Re:Another scripting language? (0)

Anonymous Coward | more than 7 years ago | (#18578791)

<sarcasm>What advantage does C++, C, Pascal, other programming languages have over machine language that makes it worth investing the time to learn? Let's all go back to learning machine language and if you can't then you are just too stupid to work in Information Technology.</sarcasm>

It's an embedded data-description language (1)

Dutch Gun (899105) | more than 7 years ago | (#18578931)

There are two things that make Lua different/better than existing scripting languages, IMO:

1) It's designed to be embedded in applications.
2) It's a data-management language.

Other languages can be embedded, but it's harder to do (at least when I last looked), and I have yet to see an embedded language as lightweight as Lua with equivalent features. It also has the advantage of being a self-describing human-readable data format (plain-text), but it has an advantage that it's ALSO a language. While all languages worth their salt can embed data, Lua is *designed* around this feature. The use of tables as a built-in data type is key here.

If you like, you can think of Lua as a more flexible XML, an easily embedded scripting language, or some combination of both.

Re:Another scripting language? (1)

daVinci1980 (73174) | more than 7 years ago | (#18579017)

Lua's not bad as a very trivial sort of scripting language, but the problem with it is that you cannot extend it with structures without writing underlying C code.

That makes it a pretty poor choice to do anything that's fairly complex, because under the covers you're still going to write a significant amount of C. All the flexibility of a scripting language, all the danger of C code is not a place I like to spend my time.

Lua is a tiny, tiny scripting language, which is pretty cool. However, it also has an equivalently tiny standard library. For the same 181K, I can get python embedded in my application. (I can then add pieces, ala carte, from the standard library).

Most newer game engines are using python (or something with a very similar featureset) for their scripting needs as opposed to lua.

Re:Another scripting language? (1)

grumbel (592662) | more than 7 years ago | (#18579433)

### What advantage does Lua have over perl/python/ruby/other existing scripting languages that makes it worth investing the time to learn?

When it comes to day to day scripting, I don't think its worth to learn, since it just doesn't provide much in that area, its just not what is was build for. What LUA however is very good at is getting embedded in other applications, in that area it just is way superior to perl/python/ruby/etc.

Its not just a matter of size, but mainly a matter of flexibility, i.e. if you want to run multiple VMs at once (say one for each game object), then you can simply do that in LUA, in other scripting languages you however can't do it at all or only with dirty hacks. The reason is that most other scripting languages are not meant to be embedded, but to run stand alone, their APIs just aren't build with that flexible in mind. Perl/Python/Ruby/etc. are for most part build so that you give control up to their interpreter, while LUA is build in a way that your C code always has full control.

In a LUA based application you have C code that runs LUA scripts, in a perl/python/ruby/etc. application on the other side you have perl/python/ruby/etc. that runs C code, big difference when you just want to extent an application instead of let the script take over.

Re:Another scripting language? (1)

Luatic (1083347) | more than 7 years ago | (#18579779)

check out this benchmark [debian.org] : it'll open your eyes bigtime! (especially if you take in account that the complete language together with it's os, string and math library takes no more than 180k; which makes it a real alternative for embedded solutions)

Try out lua - on Nmap (3, Informative)

wordisms (624668) | more than 7 years ago | (#18577581)

Great example of how lua can extend the functionality of a program. Check out the Nmap Scripting Engine [insecure.org] .

With lua and NSE, nmap can now do things like vulnerability testing. Why not download nmap [insecure.org] now and give it a try?

The ignorant and SlashDot authorship... (-1, Troll)

xxxJonBoyxxx (565205) | more than 7 years ago | (#18577583)

Brazil is no longer just on the map for it's fine coffee and martial arts.


Umm...
Mardi Gras? Nazi hideout? Amazon rainforest? Soccer? And that's not even trying...

Re:The ignorant and SlashDot authorship... (1)

StarfishOne (756076) | more than 7 years ago | (#18577611)

"And that's not even trying..."

Yeah, you forgot the women. ;)

Re:The ignorant and SlashDot authorship... (1, Funny)

Anonymous Coward | more than 7 years ago | (#18577765)

He didn't forget: he's a /. nerd, so clearly women never entered his mind.

Re:The ignorant and SlashDot authorship... (1)

StarfishOne (756076) | more than 7 years ago | (#18578915)

Hmm, that's one point of view.. another one is that nerds have to keep track of ALL variables. :D

Re:The ignorant and SlashDot authorship... (1)

p3d0 (42270) | more than 7 years ago | (#18577783)

Yeah, I agree. That was lame, lame, lame.

Re:The ignorant and SlashDot authorship... (4, Insightful)

vivaoporto (1064484) | more than 7 years ago | (#18577845)

As a Brazilian, I can say you are really not trying.

Mardi Gras?

There is no such thing in Brasil. I guess you mean carnival [wikipedia.org] , it differs from mardi-gras in the ammount of naked people (and crossdressers).

Nazi hideout?

I think you confused Brazil with Argentina [wikipedia.org] . A lot of criminals flees to Brasil, a lot are born there, but Nazi is not really our specialty, as our ethnic diversity would easily get them mad and bust their covers.

Soccer?

We don't know this sport there. But we are five times champions of Football (Association), if that is what you mean. (Tongue in cheek)

Regardless of that, I agree with your take, Brasil is not known only by its fine coffee and Martial Arts. It is not even known by it's Martial Arts, for god sake, except for people that follows MMA and know that Brazilian Jiu Jitsu exists (we in Brazil don't call it that, we call it only Jiu Jitsu).

The general sensation in Brazil is that we are known by our futebol, our samba and carnival, our giant man-eater screaming snake overlords (anacondas), our monkeys and our natural beauties (landscapes and women).

Re:The ignorant and SlashDot authorship... (0)

Anonymous Coward | more than 7 years ago | (#18578135)

Regardless of that, I agree with your take, Brasil is not known only by its fine coffee and Martial Arts. It is not even known by it's Martial Arts, for god sake, except for people that follows MMA and know that Brazilian Jiu Jitsu exists (we in Brazil don't call it that, we call it only Jiu Jitsu).

MMA is pretty popular in the states. Pre-MMA days, the first things I thought of when I heard Brasil was the Soccer team and hot women. Now I think of BJJ first, because BJJ was just that dominant in the early UFCs. As for martial artists not knowing BJJ outside of MMA, I have an article about Helio Gracie being in the longest fight ever from a Karate magazine around 1990, before the first UFC in America. I have to admit, I had no idea what to think when I read it as a kid, other than it had to be a boring fight. :)

Re:The ignorant and SlashDot authorship... (0)

Anonymous Coward | more than 7 years ago | (#18578341)

There are other things that Brazil should be known for...

1.) They are the nicest people one would ever want to meet, with qualities rarely found in North America such as humility, and spontaneous warmth and friendliness.

2.) They make excellent beer.

3.) Massive government corruption... In spite of the fact that perhaps up to two thirds of all politicians at all levels of government are corrupt, Brazilians vote them back into power time and time again. Though Brazilians can always get up a crowd to demonstrate against George Bush (who has nothing to do with this), they couldn't get off their butts to protest or demonstrate against their own corrupt leaders. They rather just complain about it and pretend that this is something beyond their control. Fiscal waste and corruption alone must be costing their GDP a good 20 percent.

4.) Brazil is totally inept at conserving its nature preserves and forests. Often there has been illegal cutting on grand scale in some forest reserve for a decade before arrests are made. Entire river systems with millions of fish are wiped out in an instant after some toxic spill. Thousands of fishermen become unemployed overnight, and people who depended on the fishery are suddenly starving and depending on handouts, but the perpetrator is never caught.

5.) Their justice system simply doesn't work very well. It takes so long to receive justice that people grow old and die before receiving fair compensation. The crooked politicians seem to never actually end up in jail. Criminals who commit heinous crimes serve little time before they are out again on holiday passes, then disappear.

6.)Oh - did anyone mention the beautiful women?

Re:The ignorant and SlashDot authorship... (0)

Anonymous Coward | more than 7 years ago | (#18578425)

It also has a VAST disparity of wealth between an elite upper class and an utterly destitute lower class.

Re:The ignorant and SlashDot authorship... (0)

Anonymous Coward | more than 7 years ago | (#18578717)

Wrong...many Nazis went to Brazil.

Re:The ignorant and SlashDot authorship... (1)

glwtta (532858) | more than 7 years ago | (#18578899)

the ammount of naked people (and crossdressers)

Doesn't that make them cross-undressers?

Re:The ignorant and SlashDot authorship... (1)

yorugua (697900) | more than 7 years ago | (#18578925)

and of course, being this slashdot, we will of course mention Brazil and recall it maybe by its coffee or Football/soccer, but not because of brazil's mulatas/garotas....

Re:The ignorant and SlashDot authorship... (0)

Anonymous Coward | more than 7 years ago | (#18578987)

It is not even known by it's Martial Arts

Umm, Capoeira?

http://en.wikipedia.org/wiki/Capoeira/ [wikipedia.org]

Re:The ignorant and SlashDot authorship... (2, Funny)

obarel (670863) | more than 7 years ago | (#18579573)

... Brazilian Jiu Jitsu exists (we in Brazil don't call it that, we call it only Jiu Jitsu).

Obligatory Simpsons' quote:

Homer: I have a bladder the size of a Brazil nut.
Taxi Driver: We just call them nuts here.

Re:The ignorant and SlashDot authorship... (1)

niloroth (462586) | more than 7 years ago | (#18577883)

Yeah, the soccer was a definite miss, but for those of use who think a work out is more than just moving a desktop from one cubicle to another, brazilian ju-jitsu is not only a great workout, but one of the best and most usable martial art out there. I would say that with the rise of MMA in this country, more Americans would relate BJJ with Brazil than soccer.

(yes, this is an Americentric post)

Re:The ignorant and SlashDot authorship... (1)

Chysn (898420) | more than 7 years ago | (#18578181)

...plastic surgery...

Re:The ignorant and SlashDot authorship... (2, Insightful)

hampton (209113) | more than 7 years ago | (#18578183)

Don't forget waxes!

Supreme Commander (3, Informative)

maeltor (679257) | more than 7 years ago | (#18577613)

Its also used in Supreme Commander, to script a lot of the in game AI and unit actions as well as define the attributes of moddable units.

Re:Supreme Commander (2, Interesting)

ni1s (1065810) | more than 7 years ago | (#18577751)

LUA was also implemented in the Freespace 2 engine that was released some years ago to the public. http://scp.indiegames.us/news.php [indiegames.us]

Re:Supreme Commander (1)

drinkypoo (153816) | more than 7 years ago | (#18577853)

Lua is used within the Half-Life 2 modification "Garry's Mod" to add easy user scripting to HL2.

Re:Supreme Commander (0, Redundant)

Xzzy (111297) | more than 7 years ago | (#18578069)

Add World of Warcraft to the list. You may have heard of it.

The entire user interface is scripted in lua, which facilitates a huge array of user made customizations.

Re:Supreme Commander (1)

drinkypoo (153816) | more than 7 years ago | (#18578823)

Yes, I heard that wow used it 42 minutes before your comment [slashdot.org] . But thank you for playing.

Small? (2, Insightful)

shmlco (594907) | more than 7 years ago | (#18577639)

"Like anything good, it didn't take long for it to be discovered by others looking for a small and efficient scripting language."

Small and efficient? Sure, for now. But wait until the rest of the OSS community gets done with it. I give it two years tops before, like PHP, it's been "extended" with 1.67 million indecipherable functions.

Re:Small? (1)

Sneftel (15416) | more than 7 years ago | (#18578849)

Ah, but that's the beauty of it. Luiz has shown an incredible resilience against the forces of bloat. IIRC, the language syntax is actually a little simpler now than it was two years ago.

Is it only for extending things? (1)

parvenu74 (310712) | more than 7 years ago | (#18577687)

After reading over the Lua home page as well as the wikipedia entry, I'm left wondering if Lua is merely a language for writing extensions or if it's intended for building things (like, say, application frameworks?). The other thing I hope someone here can answer is this: are there no other languages designed for extending other applications? Why can't this be done in Ruby or Python or Perl or JavaScript? Not to offend the tens of Lua programmers reading this, but what's the point? What is it that Lua does better than other languages available for the task?

Re:Is it only for extending things? (2, Informative)

Nanidin (729400) | more than 7 years ago | (#18577847)

Speed [timestretch.com] and size [lua-users.org] to name a few... it's also easily integrable into C/C++ programs. The second link actually has a long list of Lua benefits.

Re:Is it only for extending things? (1)

a_ghostwheel (699776) | more than 7 years ago | (#18577899)

Ruby/Python/Perl/JavaScript are much more heavy than your average embedded Lua interpreter while still providing decent language feature set. Add to this ease of customization (practically every application that uses Lua as an embedded scripting language, customizes portions of the interpreter), ability to embed not just interpreter but precompiled scripts too and ease of interaction between Lua scripts and C/C++ host program and it becomes product with maybe not large but noticeable market niche.

Re:Is it only for extending things? (1)

ukpyr (53793) | more than 7 years ago | (#18577925)

As you can do almost anything in any language, it's all about ease of task. Ruby is great for writing complex applications in (i've found), where as bash is great for copying some files around to launch an april fools day version of my company's website via cron.

I find that when I'm writing stuff in ruby, I enjoy it a tad more, than say, perl or php. I've not measured it but I think there is a correlation between enjoyment and efficency. Maybe only in that I get sick of the project I'm working on at a later time than I otherwise would have :)

From reading some lua in WoW mods and looking at TOME code, I can see why people enjoy it for layering non-compiled configs on top of compiled engines. Just take a look, (TOME is neat as a game anyway) I'm sure you'll see the point soon enough, if not, shake your head and move along to something that does strike your fancy.

Not sure this is a point other than that, does there need to be?

Re:Is it only for extending things? (0)

Anonymous Coward | more than 7 years ago | (#18578053)

(1) It's one of the fastest scripting languages (i.e. run time stuff)
(2) It's small (see above) you can fit the compiler/interperter/runtime in 150 K
(3) It's thread safe, runs just fine in multiple threads (it has no embedded threading like Perl or Python)
(4) Works really great in embedded systems for reasons 1-3.

Re:Is it only for extending things? (1)

grumbel (592662) | more than 7 years ago | (#18579565)

### Why can't this be done in Ruby or Python or Perl or JavaScript

Can't say about all of them, but most of them only allow you a single VM, which just isn't good enough when you want to keep your scripts apart from each other and secure (i.e. in a game a users script shouldn't crash the engine or change the behavior of other unrelated scripts). In Lua on the other side you can have as many VMs as you want and you never run the risk that any scripts breaks out of its little sandbox. You might be able to replicate that effect in other languages, but in Lua its simply the normal way of doing things, while in other its either impossible or requires lots of extra effort.

Re:Is it only for extending things? (1)

obarel (670863) | more than 7 years ago | (#18579619)

I have used Lua successfully on an embedded platform for demos. It would take a day or two to write a demo from scratch once we got the infrastructure.

I've used the same infrastructure on WinCE and on OMAP without any modifications (other than pushing the GUI into the WinCE).

I couldn't have done it with python+tk/tcl in the same amount of time.

Re:Is it only for extending things? (1)

peterpi (585134) | more than 7 years ago | (#18580033)

Others have mentioned the speed and size benefits. Although it's fair to say that it is niche, within that niche it is completely dominant. It's the default choice in the games industry for the sort of code that is not best done in C (or even; not best done by a programmer).

Let's say your're working on the PSP. You've got 24MB to start with. Take away 4MB for the executable and static data, 5MB for your core geometry & textures (player, car, whatever.) 2MB for sound, half a meg or so for display lists; Before you've even started doing anything you're almost into single figures. In this situation Lua fits just fine. Anything else is a squeeze.

Also; it's just really nice to work with from the viewpoint of a games coder. For example, when you create a new runtime with lua_newstate, you pass in a callback for memory allocation. How beautifully C! No inhereted, templated classes, no overdesigned 'CLuaManager' rubbish, it's just lovely. From having never used it before, I had it compiled, linked and running scripts in a particularly pleasant and easy afternoon.

Neko (0)

Anonymous Coward | more than 7 years ago | (#18577715)

Neko [nekovm.org] 's API is much more easier to use. What exactly does Lua have that Neko doesn't?

Re:Neko (0)

Anonymous Coward | more than 7 years ago | (#18577931)

Well like ruby on rails, you get Neko in Case - Lua doesn't have anything to offer in streamlined drop programming ;)

Lua's got people using it? (1)

trimbo (127919) | more than 7 years ago | (#18578591)

We've learned over and over on this board that there's only one litmus test for a language's commercial success: whether people are adopting it and using it for business, NOT academic, purposes. Lua has been in the mainstream for game scripting for some time now.

I'm sure I'm not the only one to point it out, but (2, Informative)

MyIS (834233) | more than 7 years ago | (#18577791)

What's with the "base index of 1" array conventions in their standard library?

I love Lua, and have played around with it quite a bit, but that part of their specs always annoyed me. Interestingly, it is flexible enough to allow custom "standard lib" code that uses base index of zero. Also, custom scriptable objects can define their own conventions, including relying more on the iterator interfaces, which forces things to be theoretically cleaner.

But still, just having that even as a possibility irks me.

Re:I'm sure I'm not the only one to point it out, (3, Informative)

CastrTroy (595695) | more than 7 years ago | (#18578431)

If you look at languages like C then having an array start at 0 makes sense, because the array index is the offset from the beginning of the array. However, if you don't have pointers, it's really unintuitive to have arrays starting at 0.

Re:I'm sure I'm not the only one to point it out, (1)

metamatic (202216) | more than 7 years ago | (#18578937)

Indexes starting at 0 might be unintuitive to people who aren't programmers, but it gets rid of a lot of +1s and -1s in your source code.

Re:I'm sure I'm not the only one to point it out, (1, Informative)

Anonymous Coward | more than 7 years ago | (#18579027)

> However, if you don't have pointers, it's really unintuitive to have arrays starting at 0.

Tell that to the modulo function. Or pretty much _any_ kind of index arithmetic. Would you rather do 28*i+7*j+k to do a mapping of threedimensional indices to one-dimensional, or 28*i+7*j+k-35? What about backwards?
k = n mod 7
j = (n div 7) mod 4
i = n div 28
or
k = 1+((n-1) mod 7)
j = (((n-1) div 7) mod 4) + 1
i = ((n-1) div 28) + 1
?

Re:I'm sure I'm not the only one to point it out, (1)

Doctor Memory (6336) | more than 7 years ago | (#18579029)

if you don't have pointers, it's really unintuitive to have arrays starting at 0
Not really, I typically find that when calculating an offset into a 1-based array, I have to add one to whatever offset I come up with to compensate for the base. Using zero-based arrays tends to result in more natural solutions.

Re:I'm sure I'm not the only one to point it out, (1)

PresidentEnder (849024) | more than 7 years ago | (#18579089)

I wondered this myself, learning Java. Since Java abstracts from memory and hides pointers from us, why do array indices start with 0? However, building Tetris, I became very glad of this. (Think about the position of the blocks). I'm sure there are other reasons it makes sense....

pnuts (-1, Offtopic)

kevin_conaway (585204) | more than 7 years ago | (#18577811)

Interested java developers should check out pnuts [java.net] as an alternative.

And it won't take too long (1)

Colin Smith (2679) | more than 7 years ago | (#18577851)

to turn it into a bloated monstrosity because it would be so much more useful if it just did this one tiny little additional thing.

 

Re:And it won't take too long (0)

Anonymous Coward | more than 7 years ago | (#18578143)

Actually, Lua tends to get less features with each version. The authors remove features and replace them with simpler, more powerful ones.

Why bother? (1)

SanityInAnarchy (655584) | more than 7 years ago | (#18579961)

It's embedded. Thus, any features you want to add, you'd add to your main app and call them from within Lua.

Cue the toilet humor (2, Insightful)

rrohbeck (944847) | more than 7 years ago | (#18577935)

>'Lua' means 'moon' in Portuguese and is pronounced LOO-ah.

I guess all the Americans here didn't get it.

Re:Cue the toilet humor (1)

drinkypoo (153816) | more than 7 years ago | (#18578847)

I'd guess that most of the Americans here know that while we call our toilets John, you backwards brits call them Lou.

Martial Arts? (0)

Anonymous Coward | more than 7 years ago | (#18577999)

Brazil is famous for martial arts? WTF?

Re:Martial Arts? (0)

Anonymous Coward | more than 7 years ago | (#18578039)

Brazilian Ju-Jitsu and Capoeira

Step up to Lua (1, Insightful)

Anonymous Coward | more than 7 years ago | (#18578305)

Having spent many years with Perl, then Python, and finally Ruby, I discovered Lua recently at v5.1, and *love* the language. Lots of people already mentioned that it is used heavily as an embedded language, but, it was designed as an 'extensible' language, lending itself to creating DSLs with ease. One of the fastest scripting languages, it is also one of the smallest: the whole distribution fits on a floppy disk (if you still use those).
Although there is good progress with the Kepler project, there is not yet a sparkly project like 'Rails' that actively promotes the language.

Re:Step up to Lua (0)

Anonymous Coward | more than 7 years ago | (#18580055)

Ah that explains it. I don't use floppy disks anymore, needed 4 DVD's just to store "helloworld.lua"

Some thoughts on Lua (2, Informative)

ballmerfud (1031602) | more than 7 years ago | (#18578669)

I got on the Lua bandwagon last year, and for what it is designed to do, it is quite good.

Before I start cheerleading, some comments on the book. Beginning Lua Programming (BLP) is a very good book on the subject, especially for people new to Lua or perhaps even to programming. I own this book as well as the "Programming in Lua" (PIL) book by Roberto Ierusalimschy, the latter of which I think has some of the best technical writing I've seen in a computer book and is on par with the likes of the late W. Richard Stevens. The two books are both very good, but I think serve slightly different audiences. BLP is a comprehensive book filled with gradual, well thought-out examples that can pretty much lead anyone through Lua regardless of programming experience, and help them to learn it well. The PIL book is written for more experienced/professional programmers who don't need as much hand holding.

Despite being a small language, Lua sports some serious language features, and you will be sorry not to learn them all. This is where the two books differ I think. PIL assumes at least a nodding acquaintance with concepts such as closures, iterators, generators, and more advanced concepts such as its coroutines (which are a somewhat extended form of blocks in Ruby). If you are not familiar with these, BLP will ensure that you come away with a full understanding through a battery of examples and patient prose.

That said, people who are already familiar with the above (through prior experience with languages such as Ruby or Python, for example) might find BLP a little slow. This is where PIL really shines. PIL is an extremely well-written book by the Lua's principle architect which provides a full treatment of the language in an economy of pages. It is hard to believe when reading the text that English is the author's second language. The examples are all very good, well chosen, but not excessive. The book moves at a steady pace and covers the same ground in much less space than BLP. One place where PIL really shines is on covering the C API and C programming aspects of Lua. In this respect, it is clearly superior to BLP. But again, you have to be a well-grounded C/C++ developer to appreciate this.

As I said, I own them both. I read PIL first which got me embedding Lua in C applications in no time, and then went back and read BLP to round out and sharpen my skills in the language proper. I think the books can complement each other in this way. They are both above average books.

And now for those who have not used Lua and wonder why they would want to. Lua is a tiny, standalone language/interpreter that can be put almost anywhere. It is an ideal way to extend your application as the entire language and libraries fit into a single library under 200Kb in size. It is written in ANSI C and is extremely portable. In my opinion, Lua is not a language you would choose instead of Ruby or Python (unless of course you were already very proficient at it), as I think those languages have much more to offer in either syntactical elegance or extensive standard libraries. Lua's function as a language is very similar to SQLite's function as a database. It's a powerful little multitool you can use to dramatically enhance and extend your applications with very little effort. A feature that might take 3,000 lines of C might take 10 lines of Lua. My experience with it so far has been very positive, and it has pretty much become a staple in my programming repertoire. It is the ultimate compact domain specific language.

Too heavy... (1)

frank_adrian314159 (469671) | more than 7 years ago | (#18578701)

The syntax is just way too overblown - but then us Smug Lisp Weenies [c2.com] know that anything more than parens and a few lexical markers is overblown.

Re:Too heavy... (0, Flamebait)

rubycodez (864176) | more than 7 years ago | (#18579123)

yup, that link shows what the problem is with LISP. In ivory tower theory, a beautiful and indeed the most powerful possible computer language. In practice, the real world implementations that people can get and use suck, especially CL. Sad really.

Adobe Lightroom (0)

Anonymous Coward | more than 7 years ago | (#18578709)

btw, A big chunk of Adobe Lightroom's UI was written in Lua. You can google for more information.

YANSL (1)

sycodon (149926) | more than 7 years ago | (#18579429)

Another scripting language to do what the other bajillion could do with a few libraries.

AHHHHH! When will it end!?

The problem with lua... (1, Informative)

Anonymous Coward | more than 7 years ago | (#18579557)

Lua is a great little language, unfortunately the runtime changes drastically between versions. While this keeps it small, powerful and fast (especially Mike Pall's luajit) it means your apps are going to have a limited lifespan on supported runtime.

If the developers could at least maintain ABI stability so library bindings work between versions then we'd see lua gain serious traction outside of gamedev. The luajit gives mono a run for it's money in shootouts, [debian.org] and register based VMs are better suited to dynamic languages. [debian.org]

What? (1)

RoboStone (964500) | more than 7 years ago | (#18579743)

How could you all forget about Garry's Mod? Basically a bunch of in game mods are built from Lua along with custom weapons and tools.

garrys mod (1)

DuroSoft (1009945) | more than 7 years ago | (#18579917)

Lua is also used in garry's mod (Valve Source Engine physics sandbox mod)

The Important Question is (1)

johansalk (818687) | more than 7 years ago | (#18580003)

What advantage does Lua have over Scheme?
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