"glider loop" for single-glider-only oscillators, or no?

[confocaloid]

Jubjub shuttles are irrelevant to the discussion in recent posts.

The recent posts are about oscillators where the glider follows two different paths in two directions. I don't think those should be described as loops, either, unless the lanes are far enough from each other so that gliders can go in both directions at once without colliding. But in any case that is a separate question, with same-lane reflectors not relevant.

Unfortunately the rest of the reply is not specific enough. I don't understand what you mean by 'periodic connotations' or what you think LifeWiki claims to be correct.

Yes. Jubjub loops can be adjusted, and both relay and shuttle have periodic connotations. Glider loop seems more correct for this. The lifewiki also said that this is correct.

[confocaloid]

(unless two 90-degree reflectors get artificially classified as a 180-degree reflector, at least!)

I cannot understand what exactly is artificial about that. Two 90-degree reflectors can make a perfectly valid 180-degree reflector.
In fact, the most natural (and hence least artificial) way of building 180-degree reflectors I can see, is to connect two small 90-degree reflectors (e.g. two Snarks, or two bumpers, or a bumper or a bouncer).

I think any 180-degree rotationally symmetric single-glider loop can be naturally described as a shuttle. (Including rectifier loops, NW-2T16 reflector loops, four-Snark loops.)
Of course, shuttles that are too narrow to be made into loops (including "same-lane" shuttles) are shuttles too.

[dvgrn]

Two 90-degree reflectors can make a perfectly valid 180-degree reflector.
In fact, the most natural (and hence least artificial) way of building 180-degree reflectors I can see, is to connect two small 90-degree reflectors (e.g. two Snarks, or two bumpers, or a bumper or a bouncer).

I think any 180-degree rotationally symmetric single-glider loop can be naturally described as a shuttle. (Including rectifier loops, NW-2T16 reflector loops, four-Snark loops.)
Of course, shuttles that are too narrow to be made into loops (including "same-lane" shuttles) are shuttles too.

I definitely agree with everything in the above quote, except for the "too narrow to be made into loops" part. That seems like an arbitrary extra condition for loop-ness, so please can we just drop that extra criterion? For any case wider than the degenerate width-0 case, the center of a shuttled glider travels in a loop -- back on one lane and forth on a different lane.

I didn't explain "artificially" very well, in

A) there's no "back and forth" going on here (unless two 90-degree reflectors get artificially classified as a 180-degree reflector, at least!)

This was related to the "back and forth" wording in Loop (disambiguation). I'd like to keep that wording where it is, because there doesn't seem to be any broad agreement that that is an error.

The point that I was trying to make was that the p720 glider loop example from my last quote could corrrectly be described as

"two 180-degree reflectors, with a glider shuttling back and forth between them".

But that's a bit artificial, because there's no reason to ignore the composite structure of the 180-degree reflectors. It seems more natural to describe the pattern as

"four 90-degree reflectors, with a glider traveling round and round between them", or
"four 90-degree reflectors, with a glider traveling in a loop between them".

Current status
If there's eventually a community consensus that Jubjub shuttles et al. are too narrow to count as loops, then it might make sense to put something on the LifeWiki about specifically excluding that degenerate width-0 case from being a loop.

For the moment, there seems to be some disagreement even about excluding width 0, and any width wider than that definitely looks like a loop to some people.

That just means that the claim that, e.g., a pentadecathlon shuttle is not a glider loop (as well as being a shuttle) ... is controversial at the moment. That being the case, I'm thinking that existing LifeWiki contents can mostly just stay the same for the time being, since they currently don't seem to claim much of anything about whether glider shuttles count as glider loops.

I'd like to hear from anyone else who thinks that referring to Jubjub shuttles as, e.g., "adjustable glider loops", is either a bad idea or a good idea. It's still possible that a community consensus might develop on whether it's too confusing to include Jubjub shuttles as the "degenerate width-0" case in the glider-loop category.

[confocaloid]

For the moment, there seems to be some disagreement even about excluding width 0, and any width wider than that definitely looks like a loop to some people.

That just means that the claim that, e.g., a pentadecathlon shuttle is not a glider loop (as well as being a shuttle) ... is controversial at the moment.

I think my estimate at this point would be that claiming that pentadecathlon shuttles "count as loops" is significantly more controversial, not less.

It is more natural to describe pentadecathlon shuttles as shuttles. The oscillator is literally one glider shuttling back and forth (making the description match the intuitive understanding), and it is impossible to add more than one glider without having collisions (making the description 'shuttle' sufficient for such cases).

Even if you could maybe somehow make "loop" technically correct for such narrow shuttles, that wouldn't be particularly intuitive description, or a natural description, or a particularly useful description for that matter. Pentadecathlon shuttles are shuttles, not loops.

That seems like an arbitrary extra condition for loop-ness, so please can we just drop that extra criterion?

I disagree. A loop has to be wide enough to allow gliders going in both directions at once without collisions. Otherwise there can be only one glider on the long path at a time, and the oscillator can be described as a shuttle.
This is not arbitrary. This corresponds to the intuitive understanding of loops and shuttles.

[dvgrn]

I disagree. A loop has to be wide enough to allow gliders going in both directions at once without collisions. Otherwise there can be only one glider on the long path at a time, and the oscillator can be described as a shuttle.

It does not follow from this that that same oscillator can not also be described as a glider loop. My intuition says that pentadecathlon shuttles are shuttles and glider loops.

You've gone back to stating very questionable "facts", like "This corresponds to the intuitive understanding of loops and shuttles." Until someone speaks up to agree with your point of view, you're actually talking only about your own personal intuitive understanding of loops and shuttles.

I think I've explained clearly by this point that my intuitive understanding of loops and shuttles does not match yours. Now it's time to wait and see what other people say.

[confocaloid]

You've gone back to stating very questionable "facts"

Well, I think that is non-constructive. Statements like "That seems like an arbitrary extra condition for loop-ness" or "But that's a bit artificial, because there's no reason to ignore the composite structure of the 180-degree reflectors." also can easliy be classified into the same category of "questionable 'facts'".

It is obvious that everyone is stating their opinion. Sure, I could add some more extra additional words into all of my sentences, like "This seems to correspond to the intuitive understanding of loops and shuttles." or "I think this corresponds to the intuitive understanding of loops and shuttles." etc. But that would make the posts less readable, not more, and that would not change anything. (A reasonable person can understand that people here are always only stating their opinions on what is intuitive and clear, and what is unnecesarily awkward and confusing and misleading, regardless of whether or not they say "I think this is more intuitive" or just "This is more intuitive".)

I wrote "my estimate". It's everyone else's choice to either accept that estimate or not.

Also, a very simple reason to ignore the compositeness of composite 180-degree reflectors is that they are still 180-degree reflectors. And you can make a shuttle as long as desired, while keeping the 180-degree reflectors unchanged in size and mechanism. Further, the two reflectors can be put into "black boxes", excluding their internal mechanism from a design and specifying only just enough information to be able to connect them correctly.

Code: Select all

#C p800 glider shuttle
x = 122, y = 122, rule = B3/S23
27b2o$27bobo$29bo4b2o$25b4ob2o2bo2bo$25bo2bobobobob2o$28bobobobo$29b2o
bobo$33bo2$19b2o$20bo7b2o$20bobo5b2o$21b2o7$31b2o$31bo$32b3o$34bo5$3b
2o$4bo$2bo$2b5o14b2o$7bo13bo$4b3o12bobo$3bo15b2o$3b4o$b2o3bo3b2o$o2b3o
4b2o$2obo$3bo$3b2o3$11b2o$12bo$9b3o$9bo28$54bo$53b2o$53bobo$112bo$110b
3o$109bo$109b2o3$117b2o$118bo$118bob2o$110b2o4b3o2bo$110b2o3bo3b2o$
115b4o$101b2o15bo$100bobo12b3o$100bo13bo$99b2o14b5o$119bo$117bo$117b2o
5$87bo$87b3o$90bo$89b2o7$99b2o$92b2o5bobo$92b2o7bo$101b2o2$88bo$87bobo
b2o$87bobobobo$84b2obobobobo2bo$84bo2bo2b2ob4o$86b2o4bo$92bobo$93b2o!

[dvgrn]

You've gone back to stating very questionable "facts"

Well, I think that is non-constructive. Statements like "That seems like an arbitrary extra condition for loop-ness" or "But that's a bit artificial, because there's no reason to ignore the composite structure of the 180-degree reflectors." also can easliy be classified into the same category of "questionable 'facts'".

True enough -- for your second quote, anyway! For the first one I did carefully include the "seems like", to signal that that the extra condition seemed arbitrary to me.

I think what I'm really trying to say is that you repeat your opinions so often, and so confidently, and with so little room for other people to state differing opinions without getting an immediate "I disagree" ... that I really can't tell whether you think you're stating actual facts or not.

So I'm hoping that you will see your way to adding some more of those "I think" type caveats into your posts in the future, just so that it's possible to tell which statements you really do think are incontrovertible facts, and which statements are just your personal opinion but you're aware that other reasonable people might disagree.

[dvgrn]

Here's a related question from the Oscillator Discussion Thread:

Here's another shuttle-related question: was the "one or more gliders" change in this recent edit intended to refer only to things like glider-pair shuttles along the lines of the p50 glider shuttle shown in the article?

As written with the change, that sentence could now also apply perfectly well to patterns like the rectifier-loop SKOPs with multiple gliders in them ... and it even somewhat opens up the door for interpreting, e.g., an arrangement of two Snarks as a "180-degree reflector", so that generic Snark loops would go back to being "shuttles" by the LifeWiki definition.

I don't currently have an opinion on whether or not, say, a rectifier loop with a single glider should be called a "shuttle". The change was meant to include long-recognized multi-glider shuttles like the p50 glider shuttle without adding any further arbitrary restrictions that I wasn't sure would be agreed upon. I think further discussion on this topic should go in the LifeWiki discussion forum.

In this case I'd like to make some further changes. Before the latest edit, the Shuttle article said

"A [[glider]] shuttle is a shuttle in which a single glider bounces back and forth between two sides."

That correctly described single-glider shuttles, but didn't account for multi-glider shuttles like the p50 glider shuttle or the p42 glider shuttle.

Now the article says

"A [[glider]] shuttle is a shuttle in which one or more gliders bounce back and forth between two 180° reflectors."

This allows those multi-glider p42 and p50 shuttles to be shuttles -- so far so good! But it also creates some potential confusion, because it opens the door for calling multi-glider Snark loops "glider shuttles" as well, whereas that wasn't possible according to the old definition (which specifically required just a single glider).

It seems like it is possible to draw a bright line between "glider shuttle" and "glider loop" in this case:

- if the gliders travel as a unit (you couldn't remove one of them) and they all bounce off of the same side of the oscillator at the same time, then that's a single compound object (made up of multiple gliders) shuttling back and forth -- there isn't a single loop that the gliders take turns traveling around.

- if the gliders are traveling around a shared loop, and especially if you can remove one of them without affecting the other one, then "shuttle" doesn't work as well as "loop" -- because the gliders are traveling individually round and round the loop, not shuttling back and forth from one side to the other as a combined unit.

Any ideas for the clearest way to draw that line in the "shuttle" article, while still allowing both single-glider rectifier loops and multi-glider shuttles to be counted as shuttles?

Note: I'm definitely happy to move this to a separate LifeWiki Discussion thread, if it seems too confusing to mention it on this thread. It seems closely enough related to the current glider loop vs. glider shuttle topic that maybe it can be discussed here.

[confocaloid]

Here is an old example of an alien glider shuttle-

[...]
ETA²: Sparky glider shuttle.

Code: Select all

x = 28, y = 25, rule = sansdomino_s13
12bo4$12bo2$6bo3bo3bo3bo2$12bo2$21b2o3b2o$23bo$12bo8b2o3b2o4$2o3b2o5bo
$4bo7bo$2o3b2o6bo2$15bo$15bo$13b2ob2o$15bo$15bo!

Code: Select all

x = 28, y = 25, rule = B2-a/S13
12bo4$12bo2$6bo3bo3bo3bo2$12bo2$21b2o3b2o$23bo$12bo8b2o3b2o4$2o3b2o5bo
$4bo7bo$2o3b2o6bo2$15bo$15bo$13b2ob2o$15bo$15bo!

Other examples (incomplete):

p168 glider shuttle:

Code: Select all

x = 34, y = 35, rule = crawl
20bo$19bobo$19b2o$14b3ob2o$16bob2o$17bo12bo$29b3o$28b2o2bo$29b5o$31b3o
10$13bo$11b2o$12b2o$9bo$10bo2$3o$5o$bo2b2o$2b3o$3bo12bo$14b2obo$14b2ob
3o$13b2o$12bobo$13bo!

[...]
Glider shuttle:

Code: Select all

x = 27, y = 24, rule = B2e3/S23-jq
9b3o$10bo$10bo2$8bo3bo$7bo5bo2$5bo$4bo21bo$o24bo$3o7b2o9bo$o11bo8b3o$
4bo5b2o9bo$5bo19bo$26bo4$13b3o$14bo$14bo2$12bo3bo$11bo5bo!

[...]

p32 glider shuttle and 'juggler':

Code: Select all

x = 112, y = 53, rule = B2e3aceij5-ijr/S23-a4
26bo58bo$25b3o56b3o$25bobo56bobo4$20b2o9b2o46b2o9b2o$21bo9bo48bo9bo$
21b2o3bo3b2o48b2o3bo3b2o$22bob2ob2obo50bob2ob2obo$21b2obo3bob2o48b2obo
3bob2o$21bo2bo3bo2bo48bo2bo3bo2bo$20b2o2bo3bo2b2o46b2o2bo3bo2b2o$24b2o
b2o54b2ob2o$26bo58bo6$6bo5bo27bo5bo18bo5bo27bo5bo$6b3ob3o27b3ob3o18b3o
b3o27b3ob3o$8b3o31b3o22b3o31b3o2$9b5o25b5o24b5o11b2o12b5o$b2o6bo3bo25b
o3bo6b2o8b2o6bo3bo11b3o11bo3bo6b2o$2o6bo5bo23bo5bo6b2o6b2o6bo5bo12b2o
9bo5bo6b2o$b2o6bo3bo25bo3bo6b2o8b2o6bo3bo13b2o10bo3bo6b2o$9b5o25b5o24b
5o25b5o2$8b3o19b3o9b3o22b3o19b3o9b3o$6b3ob3o17bo9b3ob3o18b3ob3o17bo9b
3ob3o$6bo5bo17bo9bo5bo18bo5bo17bo9bo5bo6$26bo58bo$24b2ob2o54b2ob2o$20b
2o2bo3bo2b2o46b2o2bo3bo2b2o$21bo2bo3bo2bo48bo2bo3bo2bo$21b2obo3bob2o
48b2obo3bob2o$22bob2ob2obo50bob2ob2obo$21b2o3bo3b2o48b2o3bo3b2o$21bo9b
o48bo9bo$20b2o9b2o46b2o9b2o4$25bobo56bobo$25b3o56b3o$26bo58bo!

[...]

[...]
This allows now for ridiculously small oscillators of period p29+4N (2gliders shuttle, with population 14!) and p31+4N (1 glider shuttle):

Code: Select all

x = 68, y = 37, rule = B2ci3ai4c8/S02ae3eijkq4iz5ar6i7e
4$21bo21bo$15bo3bo16bo4bo$19b2o20b2o$8bo13bo6bo14bo2$9bobo4bo13bobo4bo
2$8bo13bo6bo14bo$19b2o20b2o$15bo3bo16bo4bo$21bo21bo11$11bo8bo26bo10bo
2$4bo22bo12bo24bo2$5bobo4bo6bo4bobo14bobo4bo8bo4bobo2$4bo22bo12bo24bo
2$11bo8bo26bo10bo!

[...]

Is this 17-cell p708 glider shuttle known?

Code: Select all

x = 65, y = 74, rule = B2-a/S12
63bo$63bo4$61bo$64bo$59bobo2bo46$18bo$19b2o12$4bo$4bo4$2bo$5bo$obo2bo!

I guess these posts provide some additional evidence, that various people preferred the word 'shuttle', when they talked about glider shuttles in actual non-meta discussions about CA patterns. Which probably means the word was a natural choice.

[Haycat2009]

Well, these are not gliders. If one part is incorrect, can we even verify that they count in this discussion?

Here’s the thing: p4 bouncer loops are shuttles and relays. Pentadecathlon shuttles are shuttles and relays. But both are periodic, so naturally Jubjub shuttle is wrong, as it is not periodic. Same for galumphers.

[confocaloid]

Well, these are not gliders. If one part is incorrect, can we even verify that they count in this discussion?

Those are definitely gliders. Just not the diagonal c/4 gliders from Life. And obviously various people described them as gliders in the quoted posts.

Here’s the thing: p4 bouncer loops are shuttles and relays. Pentadecathlon shuttles are shuttles and relays. But both are periodic, so naturally Jubjub shuttle is wrong, as it is not periodic. Same for galumphers.

How the distinction between periodic support and stable support becomes relevant in the question of whether or not an oscillator is a glider shuttle?

[Haycat2009]

Well, these are not gliders. If one part is incorrect, can we even verify that they count in this discussion?

Those are definitely gliders. Just not the diagonal c/4 gliders from Life. And obviously various people described them as gliders in the quoted posts.

No offence, but it seems as if you are sharing questionable “facts”. I do not know why you think that these are gliders, but this discussion relies somewhat on them being real. If you want to post these, the wrong answers thread is better.

Also, shuttles have a periodic connotation

[confocaloid]

Read the quoted posts. They are obviously glider shuttles, and the shuttling gliders are obviously gliders.

[hotdogPi]

1. OCA can have gliders.

2. Stable 180° reflectors can be part of a shuttle. Periodic vs. stable has absolutely nothing to do with it. (I'm not taking a side on the word "loop".)

[Haycat2009]

1. OCA can have gliders.

Yes, as Gliders are not endemic, but these are not gliders.

[confocaloid]

1. OCA can have gliders.

Yes, as Gliders are not endemic, but these are not gliders.

Surely they are. Various people described them as gliders.
Further reading: https://www.google.com/search?q=gliders ... r+automata

[hotdogPi]

I appear to be outnumbered. From Discord: Mecejide, PlanetN9ne, and AlbertArmStain say those are not gliders. EvinZL says they are.

[Haycat2009]

1. OCA can have gliders.

Yes, as Gliders are not endemic, but these are not gliders.

Surely they are. Various people described them as gliders.
Further reading: https://www.google.com/search?q=gliders ... r+automata

They are not gliders, there is ONE glider ONLY and all others are either jokes or descriptions.

[confocaloid]

1. OCA can have gliders.

Yes, as Gliders are not endemic, but these are not gliders.

Surely they are. Various people described them as gliders.
Further reading: https://www.google.com/search?q=gliders ... r+automata

I appear to be outnumbered. From Discord: Mecejide, PlanetN9ne, and AlbertArmStain say those are not gliders. EvinZL says they are.

Count me as one saying those are gliders. Also count links found via Google, in particular Aperiodical (and many others as well).
https://aperiodical.com/2012/08/a-glide ... on-exists/

[dvgrn]

I appear to be outnumbered. From Discord: Mecejide, PlanetN9ne, and AlbertArmStain say those are not gliders. EvinZL says they are.

Hmm. Outnumbered on Discord, anyway.

However, there are quite a number of authoritative sources that will tell you that it's perfectly okay to call those various things "gliders" -- in the right context.

See, in particular, David Eppstein's now-offline collection entitled "Gliders in Life-Like Cellular Automata" -- still called "GliderDB" in the latest incarnation ... because "glider" has very regularly been used as a general term for things that move in cellular automata -- basically a synonym for "spaceship".

"Glider" isn't used much for Conway's Life spaceships; when we're talking about Life, we say "spaceship" for everything except CGoL gliders, and "glider" for CGoL gliders.

But in my experience, moving things in non-CGoL patterns can validly be called "gliders", and patterns that make them shuttle back and forth can validly be called "glider shuttles".

[Haycat2009]

To be clear, here's a summary of our difference of opinion. You say

In a loop, the gliders have to go around some area. If there can be only one glider running back and forth (for example when gliders travel on the same path in both directions), then it is a shuttle, rather than a loop. It is a mis-use of terminology to describe the pattern as a "loop".

... and I would say something very similar, like this:

If there can be only one glider running back and forth (for example when gliders travel on the same path in both directions), then it is a shuttle as well as a loop. It is generally not a mis-use of terminology to describe a shuttle as a "loop" -- though it might be clearer to avoid the term "loop" for the degenerate "width-0" cases where the return lane is exactly the same as the outgoing lane.

If there can be only one glider running back and forth (for example when gliders travel on the same path in both directions), then it is still a loop. It is sometimes a mis-use of terminology to describe a shuttle as a "loop" -- as shuttle has periodic connotations and jubjubs are stable and independent reflectors.

[dvgrn]

If there can be only one glider running back and forth (for example when gliders travel on the same path in both directions), then it is still a loop. It is sometimes a mis-use of terminology to describe a shuttle as a "loop" -- as shuttle has periodic connotations and jubjubs are stable and independent reflectors.

@Haycat2009, you keep saying that "shuttle has periodic connotations". It's really unclear to me what you mean by that -- and I'm not the only one who is confused:

I don't understand what you mean by 'periodic connotations' ...

There definitely isn't any requirement that the end caps for a shuttle pattern have to be sparkers as opposed to stable objects.

Originally shuttles had to be supported only by stable objects. That limitation has long since been dropped, but it's still a perfectly valid option.

[azulavoir]

Here's a fun middle ground that calls back to the etymology:

A glider is any small, natural, glide-reflective spaceship in a rule. Small spaceships that don't flip around during their motion period, like a hat ship or the like, aren't gliders.

[confocaloid]

Here's a fun middle ground that calls back to the etymology:

A glider is any small, natural, glide-reflective spaceship in a rule. Small spaceships that don't flip around during their motion period, like a hat ship or the like, aren't gliders.

From the intuitiveness viewpoint, I agree with the part "small, natural". Personally, I'm likely to use the word 'glider' for small common gliders. And I'm likely to use the word 'spaceship' for large spaceships (beyond loafer in CGoL, possibly including the loafer as well).

However, some will say that waterbear and Sir Robin are gliders too.

I certainly disagree with "glide-reflective". LeapLife has an oblique glider (lepa). 11life has an orthogonal c/11 glider. There is a glider on an aperiodic tiling: https://aperiodical.com/2012/08/a-glide ... on-exists/

There are many sources describing spaceships as gliders, regardless of their symmetry. Those sources cannot be ignored.

[Haycat2009]

No. The only glider is 5P4H1V1, the glide-reflective polyplet. Nothing else are gliders, no matter what you say. I do not want to make it sound like an attack, but are they really so indistinguishable that you mistake them for one and the same pattern?