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Introduction to Linden Scripting Language

Posted by CmdrTaco on Sun Feb 25, 2007 01:08 PM
from the fad-or-fantastic dept.
prostoalex writes "Dr. Dobb's Journal runs a lengthy introduction to Linden Scripting Language, the language behind avatars and their interaction in Second Life: "LSL is a scripting language that runs server-side, on a piece of software called the simulator. The simulator does just what it's name implies — it simulates the virtual world of Second Life. Each simulator runs everything for 16 acres of virtual land — buildings, physics, and of course, scripts. While you manipulate the script text in a form that is somewhat easy to read, the actual code that runs on the simulator is compiled. A compiler is a piece of software that takes the text version of the script and converts it into something that can actually run. In the case of LSL, the compiler exists within the Second Life viewer itself. In the future, it is likely that the compiler will move from the viewer into the Second Life simulators, but where the code is compiled isn't very important. What matters is that the text is converted into a form that can run on the simulators.""
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  • by excelblue (739986) on Sunday February 25 2007, @01:12PM (#18143944) Homepage
    Is this a way for Linden Labs (and possibly for others) to provide closed source scripts and objects? This seems to be a very possible thing with such technology.

    What if someone only made available a compiled copy of something? It'd be scary if you can't tell what's really going on with all the stuff.
    • Re: (Score:2, Informative)

      Yes. No. Well, sort of. You can just sell or give someone an object with compiled script. If he doesn't have rights to modify script, he don't see source code.
      • Re: (Score:3, Interesting)

        Yes. No. Well, sort of. You can just sell or give someone an object with compiled script. If he doesn't have rights to modify script, he don't see source code.

        In fact, he can't even see the object code. (Actually, SL doesn't let you obtain the object code for scripts even if you do have the right to modify them. Combine this with the fact that compilation is currently client-side, and just inspecting the source of a script someone gave you isn't sufficient to ensure it's not malicious - you need to reco
      • Re: (Score:3, Insightful)

        Who cares? Linden owns the production systems, so you're not guaranteed that execution on the simulator is one-for-one with the game.
  • by Chairboy (88841) on Sunday February 25 2007, @01:14PM (#18143952) Homepage
    Credit where credit's due, it's important to note that LSL is the first scripting language to have furry [wikipedia.org] specific classes. This is an oft-overlooked aspect of modern languages.
    • by mrcdeckard (810717) on Sunday February 25 2007, @02:14PM (#18144318) Homepage

      it's funny, i just checked out 2nd life last night -- first time since a year or two ago -- and i was pretty amazed -- the place is one big car lot or sex club. really. i guess there are two kinds of people in 2nd life now -- the people selling "sex", and the people trying to sell their objects to buy the "sex".

      it really was a cool online social experiment -- it only ultimately confirmed what we knew all along -- the internet is good only for porn and consumerism.

      now, think about this for a second. first, it's not real sex that is drawing people. it's not even imagery of real people having sex. it's interaction of poorly-rendered avatars in a virtual world. this is a testament to the power of the sexual drive in humans, and what we decide to do with our best technology..... just a friendly reminder that yes, we are doomed.

      mr c
      • ... and of course, the language lacks a "redeemLindenDollarsForRealMoney()" function.

        Even Linden Labs now admits (after the taxman commeth ... and the online gambling investigators ...) that Linden$$$ are just play tokens, with no relation to real-world currency.

        • But what is real currency? All money is fake, on a basic, fundamental level. Online games simply use faker money than usual, but with real world transactions becoming increasingly virtual, the difference between the two is becoming much more uncertain over time.

          It is in the best interest of any online world to convince the government that their money is fake, since that means they won't have to subject their servers and source code to government oversight, which would ultimately make the game much harder to implement. Most games are content to let it rest at that, since they see their money as play tokens themselves.

          Linden Labs is one of the first companies to realize that there is a value in allowing the public, if not regulators, to think otherwise. All L$ cashouts are probably, technically, at LL's discretion; to give players a true, real-world legal right to convert money would mean the government would ultimately start taking a hard look at them, since from a real-world standpoint they would start looking like a bank at best, and a potential tax dodge at worst.

          It is important to note, though, that Linden Labs' business requires that the illusion be maintained. If they actually did refuse to cash out L$, it would shake user faith in the system. Trading between real-and-virtual money may be ultimately by permission only, but to exercise that authority would be dangerous to their business, and they seem like they're in this some degree of foresight instead of hoping to make a quick buck, so L$ are still, practically, safe to buy and sell. Mostly.

      • I agree with your above post except that I would insert 'not' before 'doomed' in the last line.

        If we were incapable of finding channels for commerce and amusement in new environments, then yeah, we'd be doomed.

        Having said that, if people really buy sex on 2nd life, that's kind of sad. Not because buying sex is sad but because it suggests it's a less positive environment than, say, FurryMUCK was in the last decade.

      • You used to have to go to MUDs or MUCKs to have fake sex with your anthropomorphic wolf lover, but now you can do it in Second Life with graphical avatars and animations and everything! Please kill me now!
      • it's funny, i just checked out 2nd life last night -- first time since a year or two ago -- and i was pretty amazed -- the place is one big car lot or sex club. really. i guess there are two kinds of people in 2nd life now -- the people selling "sex", and the people trying to sell their objects to buy the "sex".
        This is why I started my web site http://www.secondseeker.com/ [secondseeker.com]. The parent poster is mostly right and completely wrong.

        All that is easy to find is sex.

        There is a lot more out there, it is just hard to find. I've spent a lot of time sailboat racing in SL. I no longer have access to a boat and I really missed it. It it the same? Certainly not. Is it better, than nothing. You bet! When I raced sailboats I was on a big boat with others, now I'm at the helm. I couldn't afford to do that in the real world.

        I hate to sound like spam but if you think sex is all that there is to SecondLife, just check out my web site, you might find something to do there that interests you. (Note, the site is supported by AdSense ads, if that offends you, please don't visit, or at least don't click on the ads!)

        Paul aka Seeker Gray

    • Is that anything like fuzzy logic?
  • by IL-CSIXTY4 (801087) on Sunday February 25 2007, @01:21PM (#18144000) Homepage
    There was talk about converting the server-side scripting engine to Mono, with huge (50x) performance gains. There was supposed to be a LSL->CIL compiler at first, then libraries for other .Net languages. Has anyone heard anything about this recently?
  • by Linker3000 (626634) on Sunday February 25 2007, @01:28PM (#18144034)
    "A compiler is a piece of software that takes the text version of the script and converts it into something that can actually run."

    Glad that's all cleared up!
  • The summary quote uses 108 words to explain that there exists a compiler for this language.
    • by jfengel (409917) on Sunday February 25 2007, @01:50PM (#18144166) Homepage Journal
      The article isn't much better. It spends a lot of time going over what most Slashdotters already know, like what an "integer" is, and very little on what's novel about a scripting language for an interactive world (or whatever you want to call Second Life.)
      • Re: (Score:2, Insightful)

        Yeah, all I'm interested in hearing about is, why is it necessary to have a special-purpose language for Second Life in the first place? Is there a good reason or is it just Not-Invented-Here syndrome? Why not use Lua [wikipedia.org] (a simple, extensible language commonly used to script games) or something instead?
    • by makomk (752139) on Sunday February 25 2007, @07:19PM (#18146806) Journal
      The summary quote uses 108 words to explain that there exists a compiler for this language.

      The compiler sucks. For example, when you define a vector, it generates three "float literal" instructions rather than one "vector literal" instruction. This means that 2 instructions and 2 bytes more code than necessary are generated for each vector literal in the code (similarly with quaternons/rotations). (Remember, there's a 16Kb per script limit for code+data.) As a second example, there are two types of instruction for transferring data from the stack to local/global variables - store and pop (which is equivalent to a store, followed by a drop). For one, the compiler only ever seems to use the "pop" variant, whilst for the other it always uses a "store; pop" pair (despite this being inefficient) - I've never seen a lone "store".

      Also, the goto is broken - due to a compiler bug/design error, only the last jump to a particualr label actually does anything. (The code for matching gotos to labels can only track one goto for each label.) This is a long-standing and well-known bug which I doubt would be difficult to fix, yet no-one's bothered.

      There are also other useful instructions which are never used (such as various dups, an instruction for setting the instruction pointer directly - making jump tables/efficient switch statements possible - and an instruction for freeing arbitrary amounts of stack quickly). The compiler never optimises anything, either. It's why I don't hold out much hope for speed improvements from Mono (and indeed, the predicted improvements mostly vanished when they started running actual LSL scripts with it.)
  • In the future, it is likely that the compiler will move from the viewer into the Second Life simulators, but where the code is compiled isn't very important.

    Well, if it is running on the simulators, the simulated humans might be given access to it, and thus being able to script their own lifes!
    Well, maybe I should try if those scripts already work on our world! :-)
  • by mrcdeckard (810717) on Sunday February 25 2007, @01:56PM (#18144190) Homepage

    hello class, this is a COM-PU-TER. computers run a set of instructions called a PROOOGRAAAM. programs are nothing but 1's and 0's. heheheh, but we don't program in 1's and 0's, we program in a language, such as linden script. another computer program, called a com-pi-ler, compiles the script into a format the computer can understand. ok, class, this is a DISK DRIVE . . .

    sheesh, i thought this was /.

    (actually, it must be -- even *I* am complaining about the summaries...)

    mr c
  • by Cereal Box (4286) on Sunday February 25 2007, @03:20PM (#18144890)
    I was expecting a tutorial on how to program an army of flying penises to interrupt a virtual press conference...
  • by FishWithAHammer (957772) on Sunday February 25 2007, @03:40PM (#18145048)
    ...or have done, really. The language is a bastard child of C, basically. Its major problem is its lack of arrays; you have a strange construct called a list that sort of does the same thing, but I really don't know why it's there instead of arrays. LSL is fairly underpowered. What I've taken to doing is using its HTTP system, though, to ping my web server, do something, and feed it back into the game. To do anything really impressive with LSL, it does seem to take an outside server to do the heavy lifting. It's kind of fun, though...
      • Re: (Score:3, Informative)

        You crazy fool, they're both linear data structures that have similar interfaces. You lose random access with lists, but you gain the ability to add an arbitrary number of elements.

        Actually, LSL's lists do have efficient random access. The main catches are that they're immutable, which means that every time you want to change anything you have to copy the list (which is, of course, limited by LSL's 16Kb memory limit), and that you can't have lists of lists. (Also, their implementation of lists isn't par