Interesting Stuff

While I’m still thinking about movie reviews, I saw A Prairie Home Companion (the movie) the other day. I give it 3 1/2 out of 4 stars, no spoiler warning →

Pirates was sold out, so I saw Superman with Emily and Jenna tonight. Although the local newspaper gave it 4 stars, I was sorely disappointed in the movie. My rating: 2 1/2 out of 4 stars, but with a SPOILER WARNING →

Tonight I played bridge with Jim for the first time in about a month. It turns out that this week is the big Aquatennial tournament, so instead of the typical 6-table game, we had a huge 25-table monstrosity that was actually split into two different flights. Some of the tables were downstairs because they ran out of room on the ground floor! Jim and I didn’t have any unusually good plays, but we were consistently above average, and ended the night with a 52% game (5th of the 14 east/west pairs in our flight). This netted us each 0.61 Silver Master Points! All the ones I have previously gotten are Black, though at my rank, color doesn’t affect anything yet (it simply denotes that I got them at a larger tournament which presumably attracted stronger competition). Jim missed bidding two slams at which he instead signed off in game (only one of which I can fault him for; the other one was quite tricky), and I misinterpreted our opponents’ bidding in one hand, overbid, and went down two doubled tricks (this was our only bottom board). Other than that, though, we had no noticeable mistakes or miscommunications! We just had solid bidding and play throughout the evening. Hurrah!

One one hand, I managed to recognize a situation for a squeeze play (this was another Vienna Coup), and executed it correctly. However, it didn’t actually work (it would have worked only if the opponent with the Ace of Spades also held the Queen of Diamonds). Still, I’m proud of myself for recognizing the situation and responding correctly to it.

Also, remember not to hold up your winners too long, even in notrump: I made 12 tricks in a notrump contract because my opponent refused to take her king the first two opportunities she had, and I didn’t give her a third. This was our only top board of the evening, since everyone else made only the 11 tricks to which they were entitled. For the non-bridge enthusiasts who aren’t familiar with this strategy, a hold-up play is when you choose not to take your winner now, and instead take it later. Assuming you are still able to take it later, you don’t lose any tricks. However, this can cut the transportation between your opponents’ hands, so that one hand has remaining winners in the suit but no longer has a way to get to them (and hence cannot cash these winners). This is a particularly useful technique in notrump contracts, where the hand that becomes void in the suit cannot get in with a ruff.

Nothing interesting has happened for nearly a week, and all of a sudden, lots of things are out there! The space shuttle Discovery appears to have launched without incident, and is on its way to take a German dude to the ISS. Former Enron executive Ken Lay died of a heart attack (note that this brought up an excellent example of why Wikipedia should not be trusted (edit: link is broken; use the WayBack Machine to see the article) as much as an actual encyclopedia, since its information is not guaranteed to be correct). Although neither of thise is particularly important news, I thought I’d add them in anyway. More importantly, North Korea had a failed missile test which has prompted much of the rest of the world to be quite alarmed. UN Security Council meetings and economic sanctions appear to be following quite quickly. The test included a Taepodong-2 missile which, if successful, could hit the west coast of the USA. It appears as though Korea will have another missile test in the near future. In Europe, the Italians are cracking down on people who supposedly helped the CIA kidnap people and transfer them to countries where they were tortured. If this is part of the alleged secret CIA torture system throughout Europe, there is a lot more to be uncovered. However, it appears so far to just be a few people. Finally, Israel has continued its incursion into the West Bank, this time attempting to stop Palestinians from firing grenades into villages. The military activity began a week ago when Palestinians kidnapped an Israeli soldier, the first such abduction in over a decade.

Right. I think that’s all for the moment… Oh! and the World Cup final seems to be Italy versus France.

Today the Supreme Court ruled that the tribunals used to try prisoners at Guantanamo Bay are unconstitutional. It’s high time the courts stepped in and said that the US needs to follow both the Geneva Conventions and its own laws about military trials. However, some people are outraged that the courts have limited the power of the Bush administration. The ruling did not indicate what should be done with the prisoners, except that the current system won’t work. Still, some groups are calling this a success, going so far as to say that this might even force the prison to close (though I doubt that will happen any time soon). The tricky thing is that most of the subsequent trials are out of the jurisdiction of US courts (including the Supreme Court). Consequently, it seems like from here on in there will be nothing that the Supreme Court can do regarding the constitutionality of the prison.

Steven Colbert brought up an interesting point last week—if we let the prisoners go (even if it’s just the ones who were originally innocent), they surely hate America at this point, and are more likely than ever to try to attack the country. and yet, if we don’t let them go, the rest of the world will grow to despise the US even more. Either way, it’s a nasty quagmire, and I doubt it will be resolved for years to come, unfortunately.

I figured out the “answer” to my TeX question from yesterday—it’s undecidable! There is no way I can get my code to perform correctly and still finish up in a finite amount of time. The way to show this is similar to the proof that the halting problem is undecidable.

A quick sketch of the proof →

Also posted to tex-latex (page can be found here)

Try typing in the following code:

x  y % two spaces between x and y

% The argument of \eatandx is ignored.
% Note the space after the x.
\newcommand{\eatandx}[1]{x }
\eatandx{z} y

The second paragraph outputted has an extra space between the x and the y. I’m pretty sure this is caused by the fact that \eatandx takes an argument. Ideally, I’d like both paragraphs to look the same in the PDF (like “x-space-y”). Is there any way for the space at the end of the result of \eatandx and the space just after it to be combined into a single space (so it looks like the two spaces from the first paragraph that turned into a single space in the output)? I don’t think \unskip has the right behavior, because \eatandx{z}y should also become “x-space-y” due to the space after the x.

I suspect that this behavior happens because TeX parses the spaces in the first paragraph with its “eyes” (to use Knuth’s term), while macro expansion occurs later (possibly in either the “mouth” or the “bowels” of TeX, I think?). This would cause the first line to become the token list “x-space-y” while the second becomes “x-space-space-y” instead. However, I have no idea how to correct this and get the behavior I want (or even if that’s possible).

Any insight would be most welcome. Thanks very much!

Today’s vision meeting totally made my day. Now that the batteries are fully charged, we can proceed: the camera works, it works beautifully, and it works simply. We got it to work with the software that FIRST gave us. We got it to work with the software developed at CMU. We got it to work with a Python script David and I wrote last week. Kick ass! We got it to move the servos, capture images, track different colors around the image, and move the servos to center the camera on a swath of color. The next step, I feel, is to get the robot’s processor to interface with the camera and do all of this (we’re currently doing it from a desktop computer). The cool thing is that the hard part of this has already been solved by this awesome dude online; we just need to look through the code and figure out how he interfaces with the TTL stuff, and we should be good to go.

Some of the robotics kids have expressed interest in learning to program the processor on the robot but have no prior programming experience. Consequently, today I held a meeting about learning C (the only language with a compiler for our processor). If you think Mudd was like drinking from a firehose, you got nothing on me. In 2 hours, I attempted to teach three kids and a mom nearly all of C. We covered

• compiling code before running it
• basic syntax: semicolons, curly braces, and their ilk
• built-in types: int, bool, char, short, long, unsigned
• variables, and declaring and defining them
• if statements, and for and while loops
• boolean logic: && || ! == etc.
• creating functions, including arguments and returning values
• header files and the actual .c files
• scoping
• precompiler commands like #include and #define
• structs, though we only covered these briefly
• pointers, including pointers to pointers, dangling pointers, and the array/pointer duality (again, kinda briefly, except their utility in affecting things outside the current scope)
• cout and cin, though again only briefly (not really necessary for programming a robot that lacks both of these)
• compiler errors
• other odds and ends that were mentioned in the sample robot drivers (extern, static, and other keywords like that)

We’ll see how much of this actually stuck, but at the time the kids seemed to understand a lot of the stuff we covered.

Looking back on it, it took me months to get the hang of all of this! Though to be fair, I was supposed to be learning this stuff and applying it to tricky situations (creating my own hash tables, memory allocators, etc) at the same time.