In the language of your choice, write a function that takes a string argument and returns a string representing the PCRE pattern that matches all anagrams of the input word. For example, if the argument to the function is “retrains”, it should return a regex pattern that matches “restrain”, “retrains”, “strainer”, “terrains”, and “trainers” as well as a bunch of strings that aren’t real words. You can assume that all characters in the input string are English letters. The length of the output string should be polynomial in the length of the input (i.e., just enumerating all possible anagrams doesn’t count, since that takes exponential space).

Also, if you haven’t seen this chestnut: write a POSIX-compliant regex pattern that matches strings of the form a* (i.e., “”, “a”, “aa”, “aaa”, etc) which have composite (non-prime) length.

…and people claim that regular expressions are only as powerful as DFAs are. :-P

1. Put on Rainy Mood
2. Pull up a fireplace on Infinite YouTube
3. Turn out the lights
4. Read my 130 year old edition of the works of Washington Irving by candlelight.

All I need now is a bust of Pallas above my chamber door.

In the meantime, here’s a word game for you. How many words can you name in 10 minutes that contain all 5 vowels? Y’s are optional but stylish. It’s okay if the words contain some vowels multiple times, or if the vowels are out of order. My word list is in the first comment.

(taken out of the freezer and photographed with a Kleenex box as a backdrop) The tops of the ice cubes are frozen, but there is still liquid water underneath. The interesting thing, though, is that one spot has risen up about half a centimeter higher than the rest. What caused this to happen? Why isn’t the surface totally flat, like it was when I put it in?

Details that may or may not be important:

• I know there is liquid water underneath because I thought there wasn’t and flexed the tray to crack the cubes loose, and some water came out and then there were air bubbles floating around under the cubes.
• I kinda over-filled the tray, so that all the cubes are connected by a thin sheet of ice that goes over the plastic dividers in the tray.
• When I filled the tray with water, there were some small bits of ice stuck in the bottom of the tray, maybe a third the size of a normal ice cube. These were left over from cubes that had cracked in two, where I used the top part but couldn’t get the bottom part out. I expect they’ll become part of the new batch of ice cubes, but I haven’t checked on that yet.

Yes, it’s about cat parasites. No, it’s actually awesome and surprisingly easy to understand.

This dude, Robert Sapolsky, is a neuroscientist at Stanford, winner of a McArthur “Genius” Award, and an amazing speaker.

I could listen to him all day long. Even his daily class lectures sound fascinating (part 1, part 2; admittedly these require more of a background in the field to fully understand).

Well, PHP has this great (read: terrible) idea in which you’re really just writing XML, and the actual code is kinda embedded within it. This means that if you add whitespace in the wrong places, it gets included in the final page shown to users. Usually this is not a problem, because in HTML extraneous whitespace gets ignored. However, if you’re writing true (non-HTML) XML (like, you’re generating an RSS feed or something), apparently the very first line of the file needs to start with <?xml ...?>, or else it doesn’t parse correctly.

WordPress has a file called functions.php, where you put miscellaneous utility functions. I had added a function to it that would append a ‘→’ to all cuts on my blog, I had responsibly surrounded it with documentation explaining what it does and how it interacts with the rest of the system, and I separated it from the previous function with a blank line so they wouldn’t run together and look like a single giant function. What I failed to realize was that functions.php is used in the stuff that generates RSS feeds, which means that suddenly the RSS feed had a blank line before the <?xml?> tag, which meant it failed to parse correctly, and broke. That’s right—I broke my website by adding documentation. This is fixed now, but it’s the dumbest problem I’ve seen in a while. If you ever design a programming language or markup language (or, heck, anything that gets parsed), please, please, for the love of Zeus allow blank lines to be added in arbitrary places without affecting the functionality.

The ads are intrusive and sucky. When I joined LiveJournal in the summer of 2004, they had what was called their Social Contract. Among other things, it said, “It may be because it’s one of our biggest pet peeves, or it may be because they don’t garner a lot of money, but nonetheless, we promise to never offer advertising space in our service or on our pages.” This is one of the reasons why I picked LJ over other blogging sites. When they were bought by Six Apart, the Social Contract disappeared. When they in turn were then bought by SUP, ads started showing up on the site. At first they were small text and image ads around the edges, and it wasn’t great but I could understand that they were trying to run a business and make money. The ads grew more and more intrusive, and now they periodically have these horrible flash-based click-through monstrosities that take over the whole page until you click through them. They use Javascript to reposition themselves to the center of the screen, which means that if I look at my blog from my phone, I can’t close the ad, because the “skip this ad” link is off the screen, and when I scroll to it, the ad repositions itself to be onscreen again, which pushes the “skip this ad” link off screen again. LJ has completely broken compatibility with smartphones, which I think is a huge problem.

LiveJournal rewrites my content. Other people have explained this better than I will, but the short version is that every time you mouse over a link here, LiveJournal surreptitiously sends it off to another website that rewrites the link to embed promo codes in it. Their main example seems to be that if I put a link to amazon.com in my blog post, it will rewrite the link so that if you buy anything after clicking the link, LJ gets a cut from your purchase. In the meantime, any personal links I’ve embedded in friends-only posts get sent off to a stranger to be inspected and rewritten. I personally have opted out of this bullshit (so you won’t see it on this particular blog), but I don’t like LiveJournal opting everyone in by default. Think of all the privacy problems Facebook has gotten recently by opting people in to sharing their stuff with advertisers; this is just another facet of that.

Search sucks on LiveJournal. You can’t search your journal, and Google has trouble picking up all your archives, so it’s nontrivial to search through them. To work around this, I’ve been preemptively tagging my posts with all possible words I might search for, so that I can just try typing in a tag, and I usually get what I was looking for. but there’s an artificial limit of 1000 tags per journal, and I’ve been bumping up against that for a long time (periodically I need to go through and delete the rare tags that I would never actually search for). By moving my blog elsewhere, I can finally get decent search capabilities.

LiveJournal has a reputation of being full of whiny emo wusses. That’s not what my blog is about, and I’m tired of people looking at the URL and assuming I do nothing but complain about how horrible my parents are because they won’t let me watch TV until after I’ve finished my homework. It’s time to get rid of these connotations.

From now on, my blog can be found at blog.coolthingoftheday.com. I’m hosting coolthingoftheday.com with DreamHost, and so far they offer everything I want and more. I’ve imported all entries from here to a WordPress setup I installed, though the import process isn’t perfect and needs some clean-up. In particular, most embedded videos need re-embedding, most posts need to be categorized, many cuts need to be redone, and some other whitespace formatting needs to be changed. but on the whole, all content (including comments) will survive.

I’m also still toying around with the CSS on the site. It currently has some known issues about putting the navigation sidebar at the very bottom of the page if your browser window is very narrow; I hope to fix this soon. If you see other issues with the formatting, please tell me.

I own all of coolthingoftheday.com, and I would like to eventually put something up on the main domain that does what its name implies. However, I don’t currently find one cool thing per day to put up, and I’m wary about starting it up without a decent backlog of cool things and a steady stream of new stuff. If you know of a cool thing, send it to suggestions@coolthingoftheday.com.

There are n people who have been given a challenge: tomorrow, a hat will be placed on each of their heads. There are n different colors of hats, and colors can be repeated (or not used at all). Everyone will be able to see the hats on everyone else’s head but not their own. No one is allowed to communicate in any way while looking at each others’ hats. Then everyone is lead away into separate rooms and each person is asked the color of their own hat. If at least one person answers correctly, the group as a whole wins (unlike the unsolved hat problem mentioned above, no one is penalized for an incorrect guess). The people can discuss strategy amongst themselves before the challenge starts, but cannot communicate in any way once anyone gets a hat.

What strategy can they use to guarantee that the group wins?

and for the pedants out there: all participants are told all possible hat colors before the challenge starts (no need to guess what the unseen colors might be), and n is small enough that all colors can be distinguished on sight (it uses less than a million different shades of blue, for instance).

Edit: to be clear on the unexpected part, not only did I not foresee this issue, I’ll wager that neither the RFID makers, nor the car designers, nor the phone designers considered this confluence, either.