03.09.11

Commacopy

Posted in programming, web at 8:16 am by danvk

At work, I often see web pages that display large numbers like so:

Including the commas in the display makes the numbers easier to read. But it does have a downside. Say you want to calculate the average number of bytes per entry. If you copy/paste the numbers above, the commas will prevent most programming languages (e.g. python or bc) from interpreting them correctly.

My coworker Dan came up with a great solution to this conundrum using CSS. Try copy/pasting these numbers over into the text box:

The commas don’t copy! Best of both worlds!

You can view source to see how it works, but let’s jump straight to the goodies:

Bookmarklet: commacopy

Unobtrusive JavaScript: commacopy.js

To use the bookmarklet, drag it to your browser’s bookmarks toolbar. If you click it, it will silently convert all numbers containing commas on the current page to the fancy copy/pasteable commas. This should really be a Chrome extension that runs on every page, but I’ll leave that as an exercise for the reader.

To use the unobtrusive JS, make a copy of commacopy.js and include it in your page via:

<script src="commacopy.js" language="text/javascript"><script>


commacopy works by converting a number like:

123,456,789


into this HTML:

<style type="text/css">
.pre-comma:before {
  content: ",";
}
</style>
123<span class='pre-comma'>456</span><span class='pre-comma'>789</span>


The commas are only present in a CSS style, rather than in the text itself. For reasons which aren’t entirely clear to me, this means that they don’t make it into the clipboard when you copy/paste them.

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03.22.10

Introducing lmnowave

Posted in programming at 12:02 am by danvk

Last Winter, a dear friend of mine moved from San Francisco to Brooklyn. With an entire continent between us, my principal crossword puzzle buddy and I looked in vain to the internet for help. Was there truly no good way to do a crossword together online?

The New York Times offered an applet, but it proved to be finicky and would only let us do the most recent day’s puzzle. A friend’s project offered hope, but only led to “Service Temporarily Unavailable”.

Enter: lmnowave!

lmnowave is a crossword puzzle gadget for Google Wave. To do a crossword puzzle with a friend, you’ll both need Google Wave Accounts.

Once you’ve got that taken care of, click this big link to get going:

lmnowave installer

You should see something like this:

Click the “Install Icon” and create a new wave. You’ll see a crossword puzzle icon in your toolbar:

Click it to add a crossword gadget. It should look like this:

If you’re using Chrome or Safari, you may get a warning about not being able to upload puzzle files. This is fine — just switch to Firefox for a minute or try one of the built-in Onion puzzles.

If you have a .puz file on your computer (perhaps from your times subscription), drag it onto the big lmnowave icon:

The puzzle will load instantly. Now drag a friend into the wave:

and you’re ready to compete or collaborate as you see fit! Each player gets his or her own color, so you can keep track of who’s filled in each square:

lmnowave is an open-source project written entirely in JavaScript. If you’d like to contribute, check it out on github. Run into a bug or have a feature request? Let me know here.

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12.26.09

Crossword Word Frequency

Posted in math, programming at 10:45 am by danvk

In a previous post, I discussed downloading several years’ worth of New York Times Crosswords and categorizing them by day of week. Now, some analysis!

Here were the most common words over the last 12 years, along with the percentage of puzzles in which they occurred:

(you can click column headings to sort.)

So “ERA” appears, on average, in about 23 puzzles per year. How about if we break this down by day of week? Follow me past the fold…

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08.08.09

Breaking 3×3 Boggle

Posted in boggle, math, programming at 10:35 am by danvk

Why is finding the highest-scoring Boggle board so difficult? It’s because there are so many boards to consider: 2^72 for the 4×4 case and 2^40 for the 3×3 case. At 10,000 boards/second the former corresponds to about 2 billion years of compute time, and the latter just two years. Just enumerating all 2^72 boards would take over 100,000 years.

So we have to come up with a technique that doesn’t involve looking at every single board. And I’ve come up with just such a method! This is the “exciting news” I alluded to in the last post.

Here’s the general technique:

1. Find a very high-scoring board (maybe this way)
2. Consider a large class of boards
3. Come up with an upper bound on the highest score achieved by any board in the class.
4. If it’s lower than the score in step #1, we can eliminate all the boards in the class. If it’s not, subdivide the class and repeat step #2 with each subclass.

Classes of Boards
By “class of boards”, I mean something like this:

The squares that contain a set of letters can take on any of those letters. So this board is part of that class:

and so is this:

All told, there are 5 * 5 * 6 * 4 = 600 boards that are part of this class, each with its own score. Other fun classes of boards include “boards with only vowels” (1,953,125 members) and “boards with only consonants” (794,280,046,581 members).

Follow me past the fold for more…
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02.24.09

Chart of time.h Functions

Posted in programming at 10:04 pm by danvk

Here’s a handy chart of the C Standard Library functions in time.h:

The ovals are data types and the rectangles are functions. The three basic types are:

• time_t: number of seconds since the start of the UNIX epoch. This is always UTC!
• struct tm: A broken-down date, split into years, months, seconds, etc. In Python, it’s a tuple.
• string: Any string representation of a time, e.g. “Wed Jun 30 21:49:08 1993″.

Generally you either want a time_t (because it’s easy to do arithmetic with) or a string (because it’s pretty to look at). So to get from a time_t to a string, you should use something like strftime("%Y-%m-%d", localtime(time())). To go the other way, you’d use mktime(strptime(str, "%Y-%m-%d")).

This library has been around since at least 1982. It’s been replicated in many other languages (Python, Perl, Ruby). We seem to be stuck with it.

Read on for my rant about why this is all idiotic.
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