grenv: Pedantic? No, it's just a logical fact......
And for all: you should stop looking for an international set of Backgammon rules, as there isn't such thing........FIDE is for Chess but for Backgammon there isn't any.......

AbigailII: Okay. Let me answer your points as directly as I can:

[For the last time. But you don't seem to be able to grasp the concept that rules should be complete, and not refering to things that aren't defined.]

I fully accept that the rules should be complete. I fully accept that the rules should be correctly implemented. There should be no ambiguity and there should be no bugs. Similarly people should always be fair and the sun should always shine when we want it to. In other words it doesn't matter what should be, it matters what is. And I am only arguing about what is - the bug and the (English) rules as written. The grey area is in what these things mean and that's what this debate is about.

So:

1) [The rules of backgammon (as stated on THIS site, not rules of backgammon defined by some other identity)]

I am talking about the rules on THIS site and no other.

2) [.. nowhere state that if it is possible to move with both die, you have to do so. (This is your MDU rule).]

There IS an MDU rule - it's the one that the Fencer-acknowledged bug fails to enforce.

3) [Considering that you have to pass if there is no legal move available (no my words - read the rules), and you call this situation "impossible moves", it seems that what you call "impossible moves" is what the rules call "no legal moves".]

The rules say that the player "must pass" if they "cannot make a legal move". The use of the word "legal" in that sentence is irrelevant. It could simply say "cannot make a move" and it would still be correct. There would be no change to the meaning, either literally or by implication.

Here's a choice for you:

3a) There is a distinction between possible and legal. It's impossible to move past a prime. Legality doesn't come into it. It's impossible to come off the bar into a closed table. It's true that there are no legal moves but that's because there are no possible moves. The impossibility of a move precludes legality; you cannot judge the legality of a non-move.

Or let's say that you can't bring yourself to agree with 3a).

3b) All impossible moves are in the illegal moves category. It should be obvious that there are possible moves which are also illegal. Illegality would then be a concept that applies to all impossible moves and some possible moves. These last constitute two separate sets.

4) [Again, the rules do not define any MDU rule.]

Correct, the rules do not explicitly define an MDU rule. We have agreed on this several times now. ;-p

5) [Therefore, the "no swapping possible if there's no legal move for the second die" isn't referring to the MDU rule, because there is NO MDU rule.]

It's quite the opposite, I would suggest. This no 'Swap dice' link shown when there's no legal move with the second die" covers two situations which I've shown are separate (see 3a) or 3b), whichever you prefer).

5a) The first is when swapping the dice makes no sense because using that dice value is impossible.

5b) The second is when swapping the dice would lead to a possible but illegal move.

6) The obvious question is "what are these classes of possible but illegal moves?". The non-MDU-compliant moves are the only known class so far. And I invite you, yet again, to come up with another because my argument will collapse if you do. Go for it! ;-)

7) The sentence must therefore imply the MDU rule.

Conclusion:

The MDU rule is a BrainKing rule that is both implied by the written rules and acknowledged as a behaviour that the backgammon server should enforce but doesn't. Non-MDU-compliant moves are therefore against the rules, illegal, not to be done, yada, yada, yada.


Let's try a different tack.

Q: Does the MDU bug exist?
A: Without a doubt. It's clearly documented in the bug tracker (and, besides, it's what triggered these debates!).

Q: Is the bug really about the MDU rule?
A: Absolutely. Both of the original instances in the bug tracker as well as Wil's new example are cases of MDU rule.

Q: If this bug is a failure to enforce the MDU rule, doesn't that mean that the MDU rule is part of the BrainKing rules?
A: As Spock would say: "Logic dictates this".

Q: But if the rule isn't explicitly stated on the rules page, doesn't that mean the rule doesn't exist?
A: No. As the previous question indicates, the existence of the bug implies the existence of the rule. It should be assumed that the written rules are lagging behind and need updating.

Q: Ah, but if the rule isn't written and there's a bug which means the rule isn't actually enforced, then surely there is NO MDU rule.
A: You can certainly argue that point but it doesn't negate the fact that the bug and the written rules imply the MDU rule.

Q: Implied? Only implied?? That's not strong enough for me!
A: Ain't nuthin' I can do 'bout that!

LOLOL.

Wil: That is the most pedantic point I've ever heard. In that example you win the game either way, so a clarification of the rules in that situation is both irrelevant and silly.

I can't think of a bearing off example where it actually matters. Even with 2 left on 2 and 3 with an opponent blocking 1, and you roll 6-1. In this case you need to move 3-2, 2-off. But even if you move 3-off you are left in the same position, so who cares?

Walter Montego: This to me means either way of moving the last man off is OK by the rules.

Not for me.. Law 17 definitely says "Law 13 applies here as in all other situations". Doesn't that mean that you cannot bear off by breaking the Law 13, "Plays must be made for both dice if possible"?

>If I use the 4 and bear my last man off, the game
>is over by Law

As I pointed out, according to Law 17 referring to Law 13, you cannot bear out with 4 without first using 1, because you CAN use both dice.

playBunny: Law 13 says:

Plays must be made for both dice if possible. Either number may be played first. If either may be played, but not both, then the higher number thrown must be played.

Law 17 states:

When in a position to bear off, you may bear off a man from a point corresponding to the number on a die thrown, or from the highest occupied point which is lower to the number indicated by a die. If a number is thrown for an unoccupied point, no man below can be borne off, using such number, while any man remains on a higher point. You are not required to bear off a man if you are able to move a man forward on the board. Law 13 applies here as in all other situations.

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXx
The authors pause here to show what ChessMaster1000 was talking about when not necessarily using all of the pips. What he said is correct according to these rules. You do not have to use the pips to maximum gain as long as you use both dice in either order. They show an example of when you would want to play it one way as compared to the other.

OK, this may or may not answer the question about how one moves his last man off the board. You guys will have to appeal to the Supreme Court while I will refer you to Law 20 in the scoring section:

A game is won by the player who first bears off all of his men.

This to me means either way of moving the last man off is OK by the rules. If I use the 4 and bear my last man off, the game is over by Law and I am no longer able to make any more moves. If I use the 1 to hit my opponent's blot and then the 4 to bear my last man off, I have again won the game and it is over. It is clear to me that both are permissable without any of this illegal move stuff I keep reading about. I could see an argument if one made an illegal move that won him the game that was against the rules, but that isn't the case here. In NFL and NCAA Football, even with the clock at zero time left, the game will continue if the defense had a penalty charged to it and the offensive side accepts the penalty. I imagine there's other sports and games that have similiar situations too.

The game's over. Now pay up, and let's get another game started. :)

playBunny: I just put the book away, but I will go get it and read what it says about this. I have the feeling that it isn't directly answered since it has no bearing on the outcome of the game, but you have me curious now. :)

Pedro Martínez: Those rules in your link are not very well written and have the feel of someone translating them from a different language. I know what playBunny means by official rules. Baseball has such a set of them. Table of contents and the various aspects of the game broken down into chapters and subsections. I've always wanted to find such a rule book for NFL rules, but have not been able too. I'm sure there's a place for Backgammon rules on the internet. I have a copy of the "Official Rules of Backgammon" in a book written by Oswald Jacoby and John R. Crawford and published in 1970. The two paragraphs before the actuals rules are:

As we said in the Introduction, back in 1931 Wheaton Vaughan, the chairman of the Card and Backgammon Committee of the Racquet and Tennis Club of New York, invited representatives of the other clubs to join with the Racquet Club in order to produce a code of laws for Backgammon. That code was soon universally adopted and accepted generally. As far as we know, Oswald Jacoby is the only member of the committeee still alive, but their laws have lasted with practically no change, and the laws presented here are essentially the same. They have been prepared in conjunction with the International Backgammon Association and the Inter-Club League of New York.
Remember that laws are made to prevent arguments, not to cause them. Never attempt to use the laws to gain an advantage.

Then it lists 34 laws of Backgammon.
1 through 6 define the game
7 through 10 define the throwing of the dice and when a player's turn ends
11 though 17 define the play and how the dice are used
18 and 19 deal with errors, in the set up or playing
20, 21, and 22 deal with scoring the game after it ends
23 through 34 deal with Chouette, which is backgammon for three or more people.

The next chapter in this book has modifications to these rules rules some people might want to play with or can be used in tournament play.

In all this I find it amazing how simple a game Backgammon is and yet how complicated the play of it can be. Good qualities in any game.

I have a saying about games, "If you can't argue about it, it usually ain't much fun to play."

playBunny: Maybe you can use some of the keywords in the paragraph in a google search and find some links that way. Since my book is over 30 years old, some of the organizations might have merged into others or gone out of business. The authors should be a good link. Rex Nihilo mentions a Walter Trice as a good source of modern Backgammon information. Try asking him if knows about a rule book or link. He gave me a link for a book store that carries Backgammon stuff. I'm sure he could help you out.

Pedro Martínez: Ah indeed. In the procedure that I outlined below the legal moves are determined even before the user is asked to move. Although I didn't include it, the list of legal moves is necessary for the no-move-possible and dice-swapping logic.

Wil: "where is the exception that makes the other legal when it breaks one essential rule of the game?"

That's why I want to see the official rules. ;-) I want to see how they define the end of the game and whether that takes precedence over the MDU rule. It's legal to take a man off with a single dice value. If that causes the end of the game and that's that, then the other dice value doesn't matter. The end is the end.

But if not, and the MDU rule is still a requirement, then would indeed be illegal to move directly off with the one dice.

Commonsense gives us the obvious answer. I'd like to see whether the official rules also see it that way.

playBunny: Thanks for the link. Lolol - it's the one I gave in my reply to you earlier

Well, maybe, but I found it from the Finnish backgammon association's pages, http://www.suomenbackgammon.fi/

The question about the tricky last move is purely philosophical, but anyway, there should be some answer to it..

playBunny: That bear-'em-all-off-first move breaks the rule.....

Exactly, you should, as Chessmaster1000 said, investigate if the move is legal first. If you allow that that the legality is investigated after the game is over, you'd have to allow "that bear-'em-all-off-first move".

Wil: Thanks for the link. Lolol - it's the one I gave in my reply to you earlier. ;-)) It's good but it's not quite as rigourous as I'd like - it's geared towards explaining how to play rather than enumerating and defining the rules (something that would tend to frighten beginners away, lol).

That bear-'em-all-off-first move breaks the rule about moving one man for each of the dice values and moving by the exact number of pips on the dice except when bearing off, when the pips may be more than required. Allowing one "illegal" move in a special circumstance where it makes no material difference to the outcome of the game doesn't mean that any illegal move is okay at any time.

playBunny: "For the sake of expediency because it doesn't affect the outcome of the game."
Yes, true, we know that the player making the last move is the winner anyway. Maybe it really doesn't matter which one the last move is..

What do you think: are both moves legal or only one of them? Why?
If both moves are legal, where is the exception that makes the other legal when it breaks one essential rule of the game?

They are not officially official, but looks the same than official to me ;-)

http://www.bkgm.com/rules.html

About bearing all out with the first roll: If we accept that the last move doesn't need to be legal, then any player could make the first move to be the last by moving all pieces out.

Thanks Pedro, I've seen that one but it's more pretty pictures than careful language. I'm after something like their tournament rules but for the game itself.

http://www.wbfonline.com/startoplay/index.html

I can't find a link to the official rules (something with lots of numbers and paragraphs and sub-clauses, lol). Does anyone have one?

Wil: For the sake of expediency because it doesn't affect the outcome of the game. Or because the last man going off the board ends the game regardless of whether there are dice values left or not.

I skipped ChessM's point about bearing off all pieces on the first roll because I didn't understand what bearing it had on anything. Care to explain?

Chessmaster1000: I think this is very clear. There is a rule: "A player must use both numbers of a roll if this is legally possible (or all four numbers of a double)." without any exceptions. Is there any other possibility than to use the both? Using only one is breaking the game rules. Why would the last move be an exception?

If the last move is allowed to be illegal, a player might bear all pieces out at his/her first move, as Chessmaster pointed out.

Chessmaster1000: Yep, you're right about that particular conversation but you wouldn't have it with me. ;-D

With me it would go:

A1. Well, firstly, I wonder what you mean by "move"? Is that a single man moved using one of the dice values or all the moves that the user sees fit to make?

If it's the single-move-at-a-time case then the 2-off would be legal and it would also end the game.

If not then the 2-off would still be legal and it, too, would end the game. The other dice value would be deemed impossible to play, which is fine.

A2. Of course!

A3. Nope. It's a valid move with one dice value legitimately discarded because it's impossible to play once the piece is off the board.

Or:

A1. Well, that's not quite how I'd do it. Mine would be:

1 - Make a list of all the possible and legal combinations of moves.
2 - Get the User's move-combination.
3 - If the User's move-combination does not match one of those listed,
....... - Inform the User.
....... - Go to 2.
4 - Make the move.
5 - If the move ends the game ...

And step 1 would include moves that use a single dice to remove the last man from the board.

If you like, I'm saying that the MDU rule has a special case for the last man. Why? Because the outcome is exactly the same except that the rigid application of the rule requires the user to make more effort to finish the game. Allowing the single move is expedient without loss of fairness.

Chessmaster1000: You are arguing what is called a moot point. The game is over and there is no recourse. Both moves are legal whether or not they logically follow from your premise.

grenv: Yes, Abigammon seems like a good name for it, though I was thinking Fencer's Backgammon would be workable too. :) I think you're right, he didn't purposely make the game play how it does, it just happens to play how it does.

AbigailII: If Fencer asks, I will indeed write up an English version of the Backgammon rules as the game is played here. And it will be clearer than what exists now, followed with examples. From what I've seen of what happens in various forced move situations, it isn't implimented consistantly. Sometimes after swapping the dice you may not be allowed swap them back. If one is aware of how this game is played on this site and is going to play it as allowed, then it is wise to check out how you want the dice played with this in mind. That is why 1-6 isn't the same as 6-1 on occasion. This is definitely a flaw in the programming and is not consistant with the playing of the game regardless of which rules we are playing the game with.

Perhaps we should just rename the game to Abigammon. Then we couldn't argue about the real rules.

If we are playing backgammon then this site is not the owner of the rules. The fact that the rules are shown here is only for the benefit of people who know not how to play. He has made a slight oversight here, similar perhaps to overlooking en passent in chess. It is an oversight, NOT a rule change.

In other words, a "legal move" as put in the English version of the BG rules refers to a move that is allowed by the BK rules, including a move that is against the MDU rule.

playBunny: For the last time. But you don't seem to be able to grasp the concept that rules should be complete, and not refering to things that aren't defined.

• The rules of backgammon (as stated on THIS site, not rules of backgammon defined by some other identity) nowhere state that if it is possible to move with both die, you have to do so. (This is your MDU rule).
  
• Therefore, the "no swapping possible if there's no legal move for the second die" isn't referring to the MDU rule, because there is NO MDU rule.
  
• Considering that you have to pass if there is no legal move available (no my words - read the rules), and you call this situation "impossible moves", it seems that what you call "impossible moves" is what the rules call "no legal moves".
  
• Again, the rules do not define any MDU rule.
  

Now, either quote the specific part of the rules that define your MDU rule, or stop using arguments that there is an MDU rule.

playBunny: Lolol re "Serious about the tricky one". Pgt is right, of course. Having legally taken the last piece off with the higher dice it is then impossible to use the other value.

Q1: Do you agree that the procedure of play at Backgammon should be :
- Making a move
- Investigating if it is legal
- Investigating if this move ends the game
A1: YES

Q2: Do you agree that the game SHOULD end with a legal move?
A2: YES

Q3: Do you agree that after 2-off the move ends illegally?
A3: YES

The above conversation implies that 2-off is an illegal move.......

So where do you have a disagreement? I guess it's on the question's 1 procedure that
should be according to you:
- Making a move
- Investigating if this move ends the game and then everything else stops and we have a winner
- Investigating if it is legal


Now don't you see that the second procedure is not so logical...........?!?!?!?

WhiteTower: Saying it's the way it works doesn't mean there's no issue but it can certainly be used to state that your exploration stop there. (Such action is just one of the options so no criticism is intended.)

Lolol. I reckon maybe he does! ;-)

playBunny: All I was saying is that, as long as the site allows you to do something, whatever the documented rules say in favour or against it, it simply is the way it works. Maybe Fencer doesn't want to change the wording in the rules, maybe he likes the controversy :)

WhiteTower: "Let's just accept ..." Lol. Why? I'm having fun debating with Abigail and my guess is that she's enjoying it too. So are some spectators. Others are bored by it and some couldn't care less. That's just how it goes.

"Let's just accept ... Fencer's rules" I wish that people would, lolol. Perhaps you've missed what this debate is about. I'm saying that, for various reasons (see below), Fencer's rules include MDU, even if a bug prevents that rule from being enforced. So accepting Fencer's rules means accepting the MDU rule. But some folks disagree with that ....

If you play against me and do what BK allows you - ie. exploit the bug to gain an unfair advantage - when it's against Fencer's rules (and I have provided evidence of that) ... what illusions are you talking about? ;-)


AbigailII: The fact that the game doesn't enforce MDU because of a bug doesn't invalidate that rule. True, MDU isn't written into the rules explicitly, but, as I have explained, it is implied by the phrase in question. Simply saying that you "doubt that" isn't providing any additional information and so I'm keen to see you provide some inkling as to what illegal moves that phrase could be referring. This is a key point in my current argument and this is the third request for you to address it but you seem unable to provide an interpretion. Without that we cannot continue this discussion (much to the relief of WhiteTower and any one else who groans with the appearance of each message, lolol)

Note that the pass situation has nothing to do with this debate as it refers to the impossibility of making a move as opposed to there being alternate possible moves, one or more of which are illegal. ;-)

Let's just accept that this is Fencer's site and the rules are as he wants them, pending any feedback that he deems reasonable and actionable.

If you want to play by any set of defined/accepted/fair/international/whatever rules, accept that you cannot do it on BK (for now)

I will keep playing according to what BK allows me and I expect my opponents HERE to do the same - and if they don't agree, well, then they shouldn't be playing under illusions, should they?

playBunny: Considering the rules don't define the MDU, nor does the game enforce it, I doubt that The player could not make a legal move with the second die refers to the MDU.

Note that the rule above mentions legal moves as well: If the player cannot make a legal move, he is notified about this situation by a message "You cannot make a move" and must pass this move to his/her opponent by performing an "empty" move - clicks on one of sending buttons. Such move is displayed as "pass" in the game notation.

AbigailII: "Then you tell me what's meant with the illegal moves in the rule that states the swap dice link won't work.". I thought that's what my post did. Was it unclear? As far as I'm concerned the swap link implies the MDU situation and no other. That's why I asked you to suggest a different kettle of fish.

Chessmaster1000: "The rule is simple without using the maximize word anyway:". Yep, but we've talked about this rule so many times that an abbreviation is required. Try saying it with just three words or less. ;-p

Lolol re "Serious about the tricky one". Pgt is right, of course. Having legally taken the last piece off with the higher dice it is then impossible to use the other value. Impossible isn't illegal - so you have a choice with that case.

Interestingly enough (and annoying, too) is that at VogClub you arerequired to use the smaller dice first before bearing off the last man. Too strong an implementation of the MDU rule, lolol.

playBunny: LOL...:)

Wil: Indeed; we have no disagreement. The maximise dice usage rule is about using the dice values, not the pips (which would be the nonexistent maximise pip usage rule).

I and others have already defined the rule in previous discussions (which you most likely haven't seen) which is why I use the shorthand rather than spell the rule out again and again.

For anyone who wants to know, here's a full version (see section Movement of the Checkers, part 4).

Pedro: Lol. Return quibble: I've declared that Fencer has defined it as a bug. ;-)

playBunny: just a minor note: it doesn't matter how many times you declare it's a bug

Pedro Martínez: the English rules should take precedence with regard to the other translations: Other translation being French, German, etc, but not presumably Czech. It was just a minor point. Why would Fencer write something in English and then translate it back to his own language? Not knowing the guy, who knows? lol. But the reason I wondered is that you've told us that the Czech version doesn't have the word legal while the English rules do, so it was a question of whether the word was lost going from English to Czech or added when going frmo czech to English, unless they were done independantly. Again, just a minor curiousity.

Quote: "I think that Fencer said somewhere that it was a bug" Lol. I don't know how many times I've declared/stated/affirmed that it is a bug, given the bug-tracker link and more ... I agree that having a bug means that it's up to the players what to do - it has to be, for the possibility to exploit it exists - but this discussion is more about what they should do; whether it is legal or not. I reckon that the fact that it's a bug means that the move in question is illegal. But I've said all this before so Ende.

playBunny: ok .. i will post it when i encounter it again :)

Hrqls: That's a separate issue and certainly a reportable bug.

Chessmaster1000:
>Then is the 2-off (using only the 4) winning the >game, a legal move?
Or do you have to use both numbers with 2-1 1-off ?
I would say the later is correct, but what's the problem, it is also a winning move?

But it's over with an illegal move (haven't used both dice numbers). We should investigate after every move if the move played was legal or not.

If we don't do that as you suggest, someone can for example in the start of the game having a 42 to play, to take all checkers claiming that he won........

So since the move 2-off is illegal the game can't be over with an illegal way.......

I'm always serious.......!

Chessmaster1000: Having played 2-off the game is over, so there is no question of using the other die. When it;s over, it's over! Surely you are not serious!

It depends of how you define maximize......
The rule is simple without using the maximize word anyway:

If you can use both dice you should do it.

If you can use only one then you should use the higher one.

If you have a double you should use the maximum number of rolls possible. 4 or else if you can't use 4 you should use 3, or else if you can't use 3 you should use 2, or else if you can't use 2 you should use 1.....

And a tricky one:
Suppose you have a single checker remained at 2-point and your opponent has one at your 1-point and you have to play 41 for example.
Then is the 2-off (using only the 4) winning the game, a legal move?
Or do you have to use both numbers with 2-1 1-off ?

Wil: maximise-dice-usage rule

I'll explain more carefully.. There are rules that require to move both dice if possible and to move bigger one if possible, but there are no rule that require to maximise the usage of dice. The example move I gave is legal regardless of the fact that the move uses only 8 pips out of the 9 possible.

Reading more carefully, I assume Abigail referred to the 'use both if possible' rule.

playBunny: Given that it's an example of the MDU rule, isn't you saying "(or at least, according to the rules, you shouldn't be able to swap the dice)" an agreement that these moves are against the rules?

No. It's just that I can't remember ever encountering the situation I described, so I don't know for sure whether the swap dice link will work or not. All I'm saying is that the rules claim the swap dice link will not work in that situation. But the proof of the pudding is the eating.

Er, that's an example of the kind of illegal move that we are already been discussing, ie. those which go against the maximise-dice-usage rule.

Whatever. Then you tell me what's meant with the illegal moves in the rule that states the swap dice link won't work. If you're going to dismiss anything as being in another class, you tell us what it means. You seem to have a good idea...

Pedro Martínez: *nod* thats how i learned about that rule .. i didnt know .. i made a move which isnt allowed according to that rule .. my opponent told me about it .. now i know .. and i play according to it and just hope my opponent does as well :) .. if not .. ah well .. its just a game :) .. its just one move in a game ... my opponent could have gotten a very useful roll as well (probably some nice doubles) instead of this one .. so it partially up to chance as well .. and might be covered again by some luck from my side :)

playBunny: those which go against the maximise-dice-usage rule

Obs! There is no such rule. That kind of rule sounds logical, but it is not part of international backgammon rules. Ie, if I have 2 pieces left, one at 4 and 5, I get 6+4, I can move the 4 first (5 to 1) and then 6 (from 5 to off). Legal move, but not very wise..

playBunny: That's interesting. I wonder which set of rules would take precedence. I believe the English ones should be primary with regard to the other translations but Czech is Fencer's language so I wonder whether the English set is a translation of the Czech, vice versa or are they independant?

Even though I don't know what you mean saying that the English rules should take precedence with regard to the other translations, I believe the rules should be interpreted in connection with what the game itself allows you and more importantly, what has been declared by Fencer on the discussion boards. To answer your question - I'm sure most of the rules were written first in Czech (since the Czech ones are more comprehensive and Czech is Fencer's mother tongue). Why would Fencer write something in English and then translate it back to his own language? As for this backgammon problem, I think that Fencer said somewhere that it was a bug and would be eventually fixed. That means it's up to the players how will they play. You say playing by the Worldwide Backgammon Federation rules shows more sport, I agree with that but if your opponent doesn't I suggest to move on, maybe mention it to your opponent in the game discussion and wait for the rule to be implemented.

alanback: Opponent has 2 stones on your 3 :)

AbigailII: Why can't you move the 4 first? You could move 7-3, 3-off or 7-3. 4-1.