From Second Life Wiki
Revision as of 14:47, 15 February 2013 by Omei Qunhua (Talk | contribs)

Jump to: navigation, search

Constant vs Explicit values?

I've noticed an ongoing style difference in recent edits, namely in the preference between named constants versus explicit values... as can be seen from difference in edits for this entry (namely 0 or PUBLIC_CHANNEL). I have no preference either way, and can see merits for both (the named constant is more informative to new users [tells what it does], the explicit value more informative to experienced users [tells what it is])... AFAIK neither compiler actually cares one way or the other so there appears not to be any side effects. should we settle on a preference?
-- Void (talk|contribs) 08:35, 27 December 2012 (PST)

My feeling was that new users are initially introduced to llSay(0, ... as that is what they are presented with from the very start with 2 occurrences in the default "new script". Using PUBLIC_CHANNEL in Wiki examples immediately adds a layer of confusion. Adding an explanatory comment each time seems like an admission that we've confused them, especially a comment that says "PUBLIC_CHANNEL has the integer value 0" ... as that is demonstrating the need to explain PUBLIC_CHANNEL rather than explaining '0' --- it's akin to a child being told "I think you'll find it easier to call me FEMALE PARENTAL HUMAN rather than Mum as that explains my role better" ... whereas Mum is what the child grew up with. SL scripters all 'grow up' with '0' as the open chat channel. I am strongly in favour of 99.9% of mnemonic constants, but 0 for channel 0 seems like a special case. For example CHANGED_OWNER is eminently more sensible than trying to remember the value 128. While we're at it, I do detest (float)FALSE and (float)TRUE ... if you really want to use TRUE and FALSE for the extremes of Alpha, then let the compiler auto-cast it for you e.g. llSetAlpha(FALSE, ALL_SIDES) but llSetAlpha(0.0, ALL_SIDES) says it much better for me and has the right flavour, as it's one value on a sliding scale. Omei Qunhua 14:31, 27 December 2012 (PST)

I'm not sure that adherence to the format of the default 'new script' does inexperienced users any favors... The default script simply a holdover from the early days of LSL, during which the only thing less friendly to inexperienced users than the language was the documentation for it =D Corey was, to put it mildly, a minimalist. There've actually been a few campaigns to get LL to replace the default (to no avail, may be buried in some fixed length record no one wants to dig up/mess with). There is no implicit understanding of what '0' means or does, or even why it's there, and the inexperienced simply repeat it cargo-cult style because it doesn't work if they omit it. it's more akin to a child calling every woman, or every parent "Mum" not knowing the relationship is specific. As for using TRUE|FALSE with things like alpha, I agree, it's generally horrible practice. As you pointed out, it's a percentage of opacity. I can't agree on relying on the compiler to autocast variables (actually it inserts a cast instruction, unless it's done in globals. even on key declarations) since there isn't a lot of consistency in what the compiler will and won't cast. it might be prettier to look at but that cast is still there whether it's documented or not, so if one must use that (admittedly horrible) structure, being explicit eliminates future subtle errors. Having that explicit cast there should serve as a warning sign

ETA: I don't usually write for inexperienced users, instead using comments for their benefit (I don't think I've ever used PUBLIC_CHANNEL myself). but that's just my natural mode, and I'm willing to work under consensus
-- Void (talk|contribs) 16:05, 27 January 2013 (PST)

I do not like PUBLIC_CHANNEL for the reason that it creates this exact problem. We aren't sure if we should use it or not. We aren't sure which is better. It's existence instead of fixing a problem created one. This is like an argument over which is better: Celsius or Fahrenheit. I don't know if we should use it in the documentation. I don't really care either way. -- Strife (talk|contribs) 21:45, 27 January 2013 (PST)

One advantage of allowing the compiler to cast an integer to a float in things like llSetTimerEvent(0), llSetAlpha(1), is that it saves bytecode space, bizarrely. Omei Qunhua 03:39, 15 February 2013 (PST)

Huh? unless something has changed drastically the compiler doesn't convert those numbers, it just inserts the cast instruction, just as if it'd been explicitly declared. It does something similar with negative numbers inserting a negation instruction instead of an actual negative number. Presumably this is for safety. Mind you that's LSO behavior, It's rather hard to pin down MONO behavior, since it's memory is assinged in blocks for functions, and can report different memory values for successive saves of event code (there seems to be some JIT insertions on run)
-- Void (talk|contribs) 08:12, 15 February 2013 (PST)
Void, I think you're not considering the full scenario. Tests just done under Mono suggest that llSetTimerEvent(0) is 3 bytes shorter than llSetTimerEvent(0.0). I suspect the reason is the excess bytecode space involved in declaring a float value of 0.0 rather than an integer of 0, which presumably is more than the inserted cast instruction. And yes, I am allowing for the 512 byte blocks of Mono allocation, by simply comparing the code size of two scripts, one containing 1024 copies of llSetTimerEvent(0) and the other containing 1024 copies of llSetTimerEvent(0.0); Omei Qunhua 13:47, 15 February 2013 (PST)