LSL Style Guide

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/LSL

Effective programming in LSL requires that developers use a disciplined approach to formatting and other conventions in their scripts.

These guidelines, referred to collectively as a Style Guide, are not as rigid as the rules required by the language compiler but nonetheless are critical to creating maintainable code. The most critical aspect of a style is that you apply it consistently to the code you write.

General Guidelines

Most people, when they start programming on their own, will have programs that are UGLY to look at; to put it nicely, sometimes mistakenly thinking that such scripts occupy less space when compiled. Such scripts typically look like the following:

<lsl> default {state_entry(){llSay(0,"Hello World.");}}</lsl>

However, that code is difficult to read (or at least to follow) when one is writing a ten thousand word program. Two common styles as to bracketing and indenting have emerged.

method one	method two
<lsl> default { state_entry() { llSay(0, "Hello World."); } } </lsl>	<lsl> default { state_entry() { llSay(0, "Hello World."); } } </lsl>

method one conserves space - IN THE SOURCE CODE ONLY, however method two is easier to read and easier to visually bracket-match. Once a scripter is in the practice of using a particular style, reading code in that style will become easier. Consistent indenting makes reading both styles easier. In both methods, indenting is the key indicating factor of levels of scope.

Naming Conventions

There are many naming conventions in Second Life. Only the most used ones will be listed below.

Global Variables (variables used through out the entire program) should be lowercase. For example:

<lsl> integer index = 0; string name = "Please set one"; </lsl>

Others prefer to distinguish between global and local variables, defining globals in the following manner:-

<lsl> integer gIndex; string gName = "Please set one"; </lsl>

Constant variables should be in ALL CAPS. For example:

<lsl> integer DIALOG_CHANNEL = -517265; vector RED = <1.0, 0.0, 0.0>; </lsl>

Arguments used within a or one of the standard events should be named with easily readable and meaningful names. When using events, please use the standard names as listed here on the official wiki. An overview of all events can be found here. Below is an example as can be found for the listen event:

<lsl> // ...

   listen(integer channel, string name, key id, string message)
   {
       key OwnerKey = llGetOwner();
   
       if (channel == 1 && id == OwnerKey)
           llOwnerSay("Hello Avatar");
   }

// ... </lsl>

Separating Code

Many people will start out doing many, many function calls on one line. This makes the code hard to read, and almost impossible to debug. The following is an example of one such program: <lsl> list lst; integer numDigits = 10;

default {

   touch_start(integer n) {
       integer i;
       integer index = llListFindList(lst, [llToLower(llGetSubString(llList2String(llParseString2List(llKey2Name(llDetectedKey(i)), [" "], []), 0), 0, numDigits - 1))]);
       if (!~llListFindList(lst, [llToLower(llGetSubString(llList2String(llParseString2List(llKey2Name(llDetectedKey(i)), [" "], []), 0), 0, numDigits - 1))]))
           lst += llToLower(llGetSubString(llList2String(llParseString2List(llKey2Name(llDetectedKey(i)), [" "], []), 0), 0, numDigits - 1));
       llOwnerSay(llList2CSV(lst));
   }

} </lsl>

Now here is the code, with the exact same features, in a simpler way. While hardly anyone could tell you what the above code did, almost everyone can tell you what the below code does.

<lsl> list listOfStrings; integer numDigits = 10;

default {

   touch_start(integer n) 
   {
       string  name       = llKey2Name(llDetectedKey(0));
       list    nameAsList = llParseString2List(name, [" "], []);
       string  firstName  = llList2String(nameAsList, 0);
       string  startPart  = llToLower(llGetSubString(firstName, 0, numDigits - 1));
       integer index      = llListFindList(listOfStrings, [startPart]);

       if (!~index)       // if index is equal to -1
       {
           listOfStrings += startPart;
       }

// send a message to the owner, only reaches owner if online and within the same sim

       llRegionSayTo(llGetOwner(), PUBLIC_CHANNEL, llList2CSV(listOfStrings));
   }

} </lsl>

LSL lacks an optimizing compiler. For this reason it may be necessary to balance the two style to get faster, more compact executable code. Line combination optimization should only be done after the code is working & bug free. Improper optimization can lead to wrong results. Always test optimized code thoroughly.

Script Structure

LSL scripts are comprised of expressions, functions, statements, event handlers and states. The LSL compiler mandates a certain structure to scripts:

1. User Defined Variables (see LSL_Variables)
2. User Defined Functions (see User-defined_functions)
3. default State (see State)
4. User Defined States

Editor

There are many 3rd party editors with LSL syntax files. See LSL Alternate Editors for more information.