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The letter of the law is inevitably subject to incomplete, or inadequate, or inconsistent, drafting.
The spirit of the law - let the opponents know what you play, to avoid gaining an inadvertent information advantage - is not.
Jan. 8
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IG, you'd be wrong.

“2.A.1 All partnership understandings, including implicit understandings and practices that arise from
partnership experience, must be fully disclosed to opponents.

2.A.2 If a player is uncertain
whether the regulations require an alert, but believes it would help the opponents, he should

If 1M-4M or 1M-(x)-4M can be a flat 3-trump 14 count - which in a strong club context they can be - of course this should be alerted. There are some people for whom this will be unexpected, since “standard” is some shapely 5-trump 6 count.

As DB is wont to say, just tell 'em what you play. Anything else constitutes an attempt to gain an unfair advantage.
Jan. 8
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I'e done this for 15 years, albeit complicated by the fact that my 2C also carries primary diamonds. For those with no such handicap, Lauria-Versace's approach is appealingly elegant and simple. From (very likely flawed) memory, after 1M-2C

2D = all 11-14 without oM (2H asks, see 2S+ below)
2H = 5+/4+ MM, any strength
2S = 15+, clubs (2NT resolves, see 3C+ below)
2NT = 15+, one-suiter (5332/6322/6331)
3C = 15+, 5M/4D
3D = 15+, 6m/4D
3H/3S = 15+, 5M/5D (lo/hi shortage)
Dec. 31, 2019
Richard Fedrick edited this comment Dec. 31, 2019
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Or three hearts for that matter: is xx Axx KQ10x AQxx supposed to pass?

Dec. 22, 2019
Richard Fedrick edited this comment Dec. 22, 2019
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Ha! Good nitpick. As it happens the existence of that Zimmerman fellow (whom I had heard discussing a certain Mr Jones the previous evening, in Philadelphia) was germane to the wording of the original post.
Nov. 27, 2019
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OK Tomasz, I'll bite. Point me to the history books that you are referring to and I will go and check as you suggest.

The history books that refer to the existence of state-funded emergency fire services, on-demand ambulance services and public hospitals (free at the point of use for individuals in a critical condition), available in a nation-state with no centralised income tax system.

You're able to do this, yes?
Nov. 25, 2019
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Charles, does your definition differ in any significant way from David’s (I paraphrase: probability is the price of a fair - aka zero expectation value of payoff - bet on some future outcome)?
This is not a rhetorical question, I’m genuinely interested (I’m not a probabilist).
Nov. 25, 2019
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‘Too much taxes’ Tomasz? I think Frances was referring to the funding source that gives us ambulance services, schools, hospitals and pot-hole free motorways. Despicable bureaucracy, all of it.
Nov. 25, 2019
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Charles, I'm sure you're right (i.e. I have no idea) about how the actual 1950s TV-show was set up. But as far as thought-experiment-MH is concerned, it undoubtedly assumes that the host will open one of the losing doors… because any other procedure is pointless (he opens nothing: game ends as there is nothing more to do; he opens the door with the golden chariot: again the game ends, as you know exactly what to do).

So yes, I think it is safe to argue that for TE-MH, the rule “the host opens a losing door” applies.
Nov. 23, 2019
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No. I understand the problem fine. The fact that the gameshow host opens a door is part of the rules of the game. It is not additional, exogenous information.
When you are planning the play as declarer, do you take careful consideration of the fact that bridge is a game played with playing cards instead of chess pieces?
Nov. 23, 2019
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That's incorrect. You don't need to “know” or “assume” he will always open a worthless door - it's the gameshow host's only rational action (opening the winning door gives you a free arb).

In the same spirit, we don't need to “assume” that a defender with QJx in trumps behind the AK will choose not to follow Q-J when you cash trumps from the top. Restricted choice is about maximising your winnings in a rational world. If the world is irrational and insists on lobbing free cash your way, you are going to come out on top anyway.
Nov. 23, 2019
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“I have a boy born on a Monday” is not the same as “I have a boy born on a particular day of the week”. The first has more informational content and therefore affects the calculation. In bridge language: if RHO opens 1H and LHO bids 3S (“heart fit and void somewhere”) this contains less information than 1H-4C (“Heart fit and a club void”). Any probabilistic calculations one might (hypothetically) make as a defender will be different in the two cases.

More generally, I don't really buy the complaints that the question is ill-posed.

(1) You are sitting in a sealed examination chamber, armed only with the knowledge that Mr Jones has two children. Given p(boy)=p(girl)=0.5, what is the chance that both kids are boys? That seems pretty unambiguous and well-posed, with a clear answer.

Then (2) some disembodied robot arm passes you a slip of paper that informs you that one of the children was born on Monday.
Does that change the calculation (aka the filtration)? Yes.
Is the problem as stated well-posed and unambiguous? Yes, as far as I can see.
Nov. 23, 2019
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Very nice and clear answer from Paul. My solution, as I was killing time at the airport was this.

We can pretend there are three genders: boy-with-some-characteristic-Q, boy-not-Q, and girl. The respective probabilities of each are q/2, (1-q)/2, 1/2

Then it’s just like throwing an asymmetric 3-sided die. Computing the probability {chance of 2 boys given at least one Q} is straightforward just by counting probabilities of all possible pairs. The result after about 2 lines of algebra and some serendipitous (*) cancellations is rather simple;

p = (2-q) / (4-q).

putting q=1/7 yields Paul’s answer, and q=1/100
Martin’s. You also get the obvious answers for q=0 or 1.

* Probably not serendipitous. When an elegant result emerges from an inelegant and clunky calculation; it usually means that there is a better and more intuitive approach available.
Nov. 23, 2019
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Are you a cosmologist by any chance?
Nov. 22, 2019
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Isn't this a hand from China? East has KQxx xxx Axx Kxx (or similar) and is strip-squeezed on the run of the hearts.
Nov. 12, 2019
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No, no, and no. Tom's OP, in essence, was an attempt to define the boundaries of ‘discloseable agreement’. This counter-example is not that.

Personally I'm astonished by the number of people lawyering away on why they shouldn't disclose stylistic tendencies. A simple 2-hour car journey after an event provides a wealth of concrete partnership understandings (“Yeah, I know a club at trick 1 beats it, but as you know I hate doubleton leads / leading low from Axxx / underleading kings / trump leads / etc) that after a while become as valid as anything documented in a written system file.

Declarer is entitled to that info*. As someone or other likes to say, ”tell 'em what you play".

*in general, but not at the critical juncture when the defender being asked the question is put in an impossibly invidious position
Oct. 23, 2019
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2NT-3; 3-3 shows four spades, or 5+4. Then

4 = four spades, nothing special
June 26, 2019
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One of us has the polarities wrong. From where I am sitting West has just followed instructions (puppeted to 3C) while his partner 2-stepped to 3NT, showing clubs along the way. No invitations involved, raise or otherwise.
March 18, 2019
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Absent UI…

a) West has seen East show a raise to 3NT with 6+ clubs and some reason for concern (presumably, spade worry)
b) East has seen West show a minimum 1NT overcall with five(+) clubs

Since we are told that East had four clubs (opposite the presumed 5+ card suit of West), I don't think that Pass is an LA - East will always bid either 3NT or 3S (which likely will fetch 3NT from West at pairs). So I allow East's actions.

As for West's actions, we don't know his hand but it would depend on whether pulling 3NT is a plausible choice. Passing 3NT would be automatic with either a double spade stopper or a club fit (e.g HHx) sufficient to suggest that East's six clubs are running; lesser holdings are more problematic.
March 18, 2019
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Terrific! I’ll give you the account details of the escrow account where you need to wire me \$10 million of cash collateral, and we’re good to go. Thanks for the trade!
June 29, 2018
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