Second Life Wiki - User contributions [en]

LSL Operators

2010-05-23T17:18:37Z

Reddot99 Republic: boolean operators have equal precedence.

{{LSL Header|ml=*}}
Operators are used to cause an operation (or mathematical action) to be performed on one (such as !) or two operands. The easy and common example is 1 + 2 where 1 and 2 are operands, and the '''+''' is the operator.

This concept can be extended much further with LSL since operands can be variables with the special case of the assignment operators requiring that the left hand side be a variable.

{| bgcolor="#FFFFFF" border="1" cellspacing="2" cellpadding="6"
|- bgColor="#A7C1F2"
! Operator
! Description
! Usage Example
|-
| () || Parentheses || a * (b + c)
|-
| [] || Brackets: list constructor || [a, 2, "this", 0.01]
|-
| (''type'') || Typecasting || message = "The result is:" + (string) result;
|-
| ! ~ ++ -- || Binary-NOT, Bitwise-NOT, Increment, Decrement || counter++;
|-
| * / % || Multiply/Dot-Product, Divide, Modulus/Cross-Product || rollover = (count + 1)%5;
|-
| - || Subtraction || one = 3 - 2;
|-
| + || Addition or joining Strings || two = 1+1;
text = "Hello" + "World";
|-
| + || Concatenation or joining Lists || myList = [1, 2, 3] + [4, 5];
newList = oldList + addList;
|-
| << >> || Left Shift, Right Shift || eight = 4 << 1;
|-
| < <= > >= || Less Than, Less Than Or Equal To,
Greater Than, Greater Than or Equal To
|| isFalse = (6 <= 4);
|-
| == != || Comparison Equal, Comparison Not Equal || isFalse = ("this" == "that");
|-
| & || Bitwise AND || zero = 4 & 2;
four = 4 & 4;
|-
| ^ || Bitwise XOR || zero = 4 ^ 4;
six = 4 ^ 2;
|-
| <nowiki>|</nowiki> || Bitwise OR || four = 4 <nowiki>|</nowiki> 4;
six = 4 <nowiki>|</nowiki> 2;
|-
| <nowiki>||</nowiki> || Logical OR || isTrue = (FALSE <nowiki>||</nowiki> TRUE);
|-
| && ||Logical AND || isFalse = (FALSE && TRUE);
|-
| = += -= *= /= %= || Assignment || four = 4;
|}

'''Note:''' Unlike most, if not all, other languages that use the C style '''&&''' and '''||''' operators, '''both''' operands are '''always''' evaluated. For example,

<lsl>if (TRUE || 1/0) llSay( 0, "Aha!" );</lsl>

will cause a Math Error rather than say "Aha".

'''Note:''' The ++ (increment) and -- (decrement) have their effect on their number either before or after the number is evaluated when used in conditions dependent on whether they are before or after the number.

<lsl>integer count;
if(!(++count)) // Is incremented then evaluated.
llSay(0, "Aha"); // Will not be said.</lsl>

<lsl>integer count;
if(!(count++)) // Is evaluated then incremented.
llSay(0, "Aha"); // Will be said.</lsl>

'''Note:''' The order of precedence of boolean operators is unclear. It is possible that there is a [http://jira.secondlife.com/browse/SVC-779 bug] in the expression parser, making precedence inconsistent, or it may simply be that '''||''' and '''&&''' have equal precedence; testing is inconclusive. Thus, when in doubt, parenthesize.
'''SubNote:''' As the above bug has been closed as expected behavior, one can only assume the boolean operators have equal precedence.

'''Note:''' The order of evaluation appears to be backwards from most languages. If the value of x starts as 1 then the first two conditions below evaluate false and the second two evaluate true:

<lsl>(x && (x = 0) == 0 && x)</lsl>
<lsl>(x && (x = 0) == 0 && x == 0)</lsl>
<lsl>(x == 0 && (x = 0) == 0)</lsl>
<lsl>(x == 0 && (x = 0) == 0 && x)</lsl>

Both sides are evaluated regardless of the the truth of either side.

{| {{Prettytable}}
|+
==+ Operator==
<code>result = left + right</code>
|-{{Hl2}}
!Left Type
!Right Type
!Result Type
!Description
|-
|integer
|integer
|integer
|Adds '''left''' and '''right'''
|-
|integer
|float
|float
|Adds '''left''' and '''right'''
|-
|float
|integer
|float
|Adds '''left''' and '''right'''
|-
|string
|string
|string
|Concatenates '''right''' onto the end of '''left'''.
|-
|list
|*
|list
|Concatenates '''right''' onto the end of '''left'''.
|-
|*
|list
|list
|Affixes '''left''' onto the start of '''right'''.
|-
|vector
|vector
|vector
|Adds '''left''' and '''right'''
|-
|rotation
|rotation
|rotation
|Adds '''left''' and '''right''' Not useful for combining rotations, use [[#* Operator|*]] or [[#/ Operator|/]] instead.
|}

{| {{Prettytable}}
|+
==Shorthand Operators==
Alternatives to the simple '=' operator...
|-{{Hl2}}
!Simple assignment operator
!Shorthand operator
|-
|a = a + 1
|a += 1
|-
|a = a – 1
|a -= 1
|-
|a = a * (n+1)
|a *= (n+1)
|-
|a = a / (n+1)
|a /= (n+1)
|-
|a = a % b
|a %= b
|}

=={{Wikipedia|De Morgan's laws|De Morgan's laws}}==
{| {{Prettytable|style=margin-top:0; float:left;}}
|+ Bitwise Equivalencies
!AND
!OR
|-
|| <code>~(a & b)</code> || <code>~a | ~b</code>
|-
|| <code>~a & ~b</code> || <code>~(a | b)</code>
|-
| colspan="2" |
|-
|| <code>a & ~b</code> || <code>~(~a | b)</code>
|-
|| <code>~(a & ~b)</code> || <code>~a | b</code>
|-
|}
{| {{Prettytable|style=margin-top:0; float:left;}}
|+ Boolean Equivalencies
!AND
!OR
|-
|| <code>!(a && b)</code> || <code>!a || !b</code>
|-
|| <code>!a && !b</code> || <code>!(a || b)</code>
|-
| colspan="2" |
|-
|| <code>a && !b</code> || <code>!(!a || b)</code>
|-
|| <code>!(a && !b)</code> || <code>!a || b</code>
|-
|}
Due to {{Wikipedia|De Morgan's laws|De Morgan's laws}}, by row, code in the '''AND''' column is logically equivalent to code in the '''OR'''. '''a''' and '''b''' need not be variables, they can be expressions. In certain circumstances these equivalencies can be used to simplify complex code. It is important not to confuse the two sets when using them. The first two rows depict De Morgan's laws as it is formulated, the second two build upon it.

{{LSLC|}}{{LSLC|Syntax}}{{LSLC|Keywords}}

Talk:LSL Operators

2010-05-23T17:11:26Z

Reddot99 Republic: /* Operator Precedence */

{{talk}}
== Operator Precedence ==

I've added a note about the precedence of '''||''' over '''&&''', and changed their positions in the table; it would be good if someone could test the rest to see if there are any other gotchas (or if, perhaps, a knowledgeable Linden could pop in here and straighten in out). I did this one as I ran into it. [[User:Siann Beck|Siann Beck]] 05:38, 6 October 2007 (PDT)

SVC-779 seems to have decided that this they have equal precedence, as that would explain the cases here,[[User:Reddot99 Republic|Reddot99 Republic]] 17:11, 23 May 2010 (UTC)

== bit shifting ==
I've been having problems right shifting negative integers and have created a function for [[Right Shift]] to bypass the >> operator and shift the signed bit. --[[User:Dedric Mauriac|Dedric Mauriac]] 02:10, 3 February 2008 (PST)

== Layout Changes? ==
Not fond of the groupings here. needs categorical groupings like Logical/comparison, math/assigment, bitwise, and maybe even grouping(to include lists) casts(possibly linked to the type pages) and concatenation.

Also Should we modify the layout to be more like other categories (types as an example) with separate pages for each operator (or perhaps just groups of operators)? There is a lot of information that I'd like to include on what types the operators work on, and differences between the returns when working on different types, and putting it all on one page is going to get messy. Thoughts?{{unsigned|Void Singer|01:16, 29 April 2009}}

PS whoops sorry about the unsigned comment, got busy between windows.

:NP. It's just an almost automatted behaviour of mine when I spot unsingned comments ^_^ [[Image:Zai_signature.png|45px]] '''[[User:Zai Lynch|Lynch]]''' ([[User talk:Zai Lynch|talk]]|[[Special:Contributions/Zai Lynch|contribs]]) 01:32, 29 April 2009 (UTC)

The article was never finished, I had ideas but never made time to finish it. If you want to work on it, by all means do. As you can see I started making operator tables but never did more than the first one. -- '''[[User:Strife_Onizuka|Strife]]''' ([[User talk:Strife_Onizuka|talk]]|[[Special:Contributions/Strife_Onizuka|contribs]]) 06:50, 30 April 2009 (UTC)

== One/Two ==
I don't understand [https://wiki.secondlife.com/w/index.php?title=LSL_Operators&curid=3817&diff=339462&oldid=293743 this correction]. I'd even consider it beeing wrong. Can anyone explain? [[Image:Zai_signature.png|45px]] '''[[User:Zai Lynch|Lynch]]''' ([[User talk:Zai Lynch|talk]]|[[Special:Contributions/Zai Lynch|contribs]]) 11:31, 29 April 2009 (UTC)
:based on [http://en.wikipedia.org/wiki/Ones'_complement this] ~(-1) = 0 in twos (this is what happens in LSL), ~(-1) = 1 in one's(this isn't). however [http://en.wikipedia.org/wiki/Bitwise_operators#NOT this] states the operator, is ones, but links to the previous, which is contradictory (probably just a mistaken redirect, but who knows)(I've heard it called both in other references, so I'm unsure if it's a matter of habit/tradition/history or which has priority). Maybe we should just call it Bitwise NOT for clarity and have done with it? (since that describes it most acurately as flipping all the bits, regardless of result) see my other comment on regrouping (ie put bitwise operators together, etc) and adding to this page, I'd love some feedback, otherwise I'm just gonna start building it in my user page space, and move it here later. [[User:Void Singer|Void Singer]] 06:22, 30 April 2009 (UTC)

::I changed the operator names to Bitwise-NOT and Binary-NOT since those are similar to the names used for CIL opcodes. Logical-NOT could be used instead of Binary-NOT and might make more sense. The link in the article as you point out is wrong, I have removed it. -- '''[[User:Strife_Onizuka|Strife]]''' ([[User talk:Strife_Onizuka|talk]]|[[Special:Contributions/Strife_Onizuka|contribs]]) 06:58, 30 April 2009 (UTC)

:::The second wiki article? or the first? I guess it all depends on if you're referring to the action or the system... where the action may be tecnically correct in the context of subtraction, the system is also technically correct in the context of the result (and less confusing IMO) [http://en.wikipedia.org/wiki/Method_of_complements ref.] (I'm preferential to Logical over Binary, since it's a more common usage, and allows better grouping)

:::PS is there a template for the extended user info you two are using for signatures? or does it just not show for my own when I'm logged in? [[User:Void Singer|Void Singer]] 18:19, 30 April 2009 (UTC)
::::In the prefrences there is a "Signiture" field that allows you to configure it. The field in preview MW versions was labeled "Nickname". -- '''[[User:Strife_Onizuka|Strife]]''' ([[User talk:Strife_Onizuka|talk]]|[[Special:Contributions/Strife_Onizuka|contribs]]) 11:33, 1 May 2009 (UTC)

== NOT assignment ==
I had trouble looking for 'NOT assignment', where some 'bootest' value would be toggled by assignment. "bootest =! bootest" correctly toggles the boolean test variable switch, but =! is not shown on this page. Was I looking on the wrong page to begin with? [[User:Romaq Rosher|Romaq Rosher]] 16:24, 7 September 2009 (UTC)

: "=!" is not an operator, it's two operators. It's Assignment and Boolean-NOT. The Boolean-NOT gets executed first. -- '''[[User:Strife_Onizuka|Strife]]''' ([[User talk:Strife_Onizuka|talk]]|[[Special:Contributions/Strife_Onizuka|contribs]]) 17:24, 7 September 2009 (UTC)

User:Nyx Linden/Office Hours Agenda

2009-08-05T19:09:58Z

Reddot99 Republic: added bug

==Nyx Linden's Office Hours Agenda==

Office hours are on Wednesdays at Noon in Pacific time (SL standard time) located in Borrowdale at: http://slurl.com/secondlife/Borrowdale/74/217/32

Topics are focused on avatars, content creation efficiency, content creation tools and methods, rendering issues, and many related random topics.

Please add topics for discussion / agenda items to the end of the list below prior to 11:50 AM. Priority will be given to topics that are posted in advance and are relevant to the goals of the office hour. Feel free to include relevant links to JIRA or wiki pages. Contact Nyx Linden if you are unsure if your topic is relevant or appropriate.

Archived agendas can be found at the [[User:Nyx_Linden/Office_Hours_Agenda_Archive|agenda archive]].

Next meeting scheduled for: August 5, 2009.

===Agenda===

==August 05, 2009==
# Avatar - bugs or 'by design' ? Deformed avatar http://jira.secondlife.com/browse/VWR-12869 Break in avatar body creating strange "joint" http://jira.secondlife.com/browse/VWR-14943 [[User:Ellla McMahon|Ellla McMahon]] 18:01, 4 August 2009 (UTC)
# Client plugins via gridproxy. Would it be possible to register external event handlers with the client so gridproxy isn't needed? What kind of events would be available? Security? Etc. [[User:Saijanai Kuhn|Saijanai]] 17:50, 5 August 2009 (UTC)
#camera bugs; VEHICLE_FLAG_DECOUPLED_CAMERA fails on nonphysical objects it seems