"Could it be? That parenthesized numeral one in the other tab can only mean that a human has sent me mail! I wonder what it could be—why, the mind staggers at the sheer number of possibilities! Could it be an old friend writing to regale me with true tales of adventure and mystery on the high seas? A professional acquaintance looking to make a business deal? Or the first of many missives to come from my destined one true love? ...

"Oh. It's the Amazon Instant Video order confirmation for the cartoon I just bought twenty seconds ago to distract me from the desperate, soul-scarring eternal loneliness.

"... exactly how many times am I going to fall for that?"

(cue Gravity Falls theme music)

Monthly Favorites, September 2015

Favorite commit message fragment: "it turns out that it's `\d` that matches a digit, whereas, counterintuitively, `d` matches the letter 'd'."

Favorite line of code: a tie, between

    let mut time_radios: Vec<(Commit, mpsc::Receiver<(Option<Commit>, f32)>)> =


        for (previous, new), expected in zip(
                itertools.product(('foo', None), ('bar', None)),
                ("from foo to bar", "from foo", "to bar", "")):

(Though both of these contain at least one internal newline, it's only for PEP 8-like reasons; they're both what we would intuitively call one "logical" line of code.)

Favorite film: My Little Pony: Equestria Girls: Friendship Games. (Poor plotting even by Equestria Girls standards, and it could only have been because of magic that I didn't get semantically satiated on the word magic during the climax. Alternate-Twilight's idiotic decision to withdraw her application to the Everton independent study program in favor of transferring to the Canterlot School of Mediocrity and Friendship in order to be closer to the Humane 5+1 was as predictable as it was disappointing—though I do credit the writers for at least acknowledging the existence of alternatives to school. And what was up with that scene where we're momentarily led to believe that alternate-Spike got switched up with Equestria-Spike in a portal accident, but then it turns out that, no, alternate-Spike just magically learned how to talk? Is it that there was no time in the script to deal with the consequences of swapping sidekicks across worlds, but that Cathy Weseluck's contract guaranteed her a speaking role? Despite being the weakest film in the trilogy (far worse than its brilliant predecessor, My Little Pony: Equestria Girls: Rainbow Rocks), Friendship Games is still a fun watch, and an easy favorite during a month when I didn't see any other feature-length films.)

From the Top

Theorem. The product of the additive inverse of the multiplicative identity with itself is equal to the multiplicative identity.

Proof. The sum of the multiplicative identity and its additive inverse is the additive identity: that is, the expression "1 + (–1)" is equal to the expression "0". Multiplying both of these expressions by the additive inverse of the multiplicative identity, then applying the distributivity axiom, the theorem of multiplication by the additive identity, and the law of multiplicative identity, we get:

–1(–1 + 1) = –1(0)

(–1)(–1) + (–1)1 = 0

(–1)(–1) + (–1) = 0

But then adding the multiplicative identity to both of these expressions and applying the law of additive inverses and the law of additive identity, we get:

(–1)(–1) + (–1) + 1 = 0 + 1

(–1)(–1) = 1

But that's what I've been trying to tell you this whole time.

No Award

Nothing should dilute or adulterate the exalted joy of watching the chess engine you've toiled over for the better part of three weekends start to suggest moves (from a basic 3-ply negamax search with a simple point-counting position evaluation heuristic), unless it's the slight(ly overdetermined?) suspicion that you're overcompensating for something, that you've proved your point by now, that bringing yet another moderately-sophisticated side project in a not-the-most-popular programming language over the threshold of "really cool-looking proof-of-concept" isn't going to show Everyone that you are Smart and should be Respected any more than the last seven already did. Some people actually use software for something other than a trophy, to automate some aspect of the world that otherwise would have been done more poorly. So you've heard. If one were to hypothesize, for the sake of argument (but perhaps not only for the sake of argument) that there can exist diminishing marginal returns to some games, that Respect from Everyone is not a real thing that can be won, that there are treasures and masteries you'd never imagine while chasing GitHub stars, much like how you know there are treasures and masteries that you'd never imagine while chasing school marks—what strategies would that imply, now that you know there is such a thing as being strategic? And how would you tell the difference?

Because People Will Have Brain-Computer Interfaces or Something

Oftentimes I awake from a coding dream with the realization that I'm physically in bed without a keyboard and that the machine is asleep in the other room, from which I can infer that I must have been asleep, too, and only dreaming about solving problems. But there will probably only be a few more decades during which not having a keyboard is evidence of anything in particular.

Studying on the Weekend

Studying on the weekend as a working professional is like keeping a diversified investment portfolio, in stocks, bonds, commodity futures, cash, silver, ammunition, and Bitcoin in encrypted paper wallets; it's like coming in first by half a lap in the thirty-two hundred meters of your Division III college's track and field meet, and then not stopping, continuing out of the stadium, desperately, bleeding, acknowledging nothing but the need to put ever more distance between you and your hypothetical pursuers, until days later (halfway to Nevada), a classmate leans out of a car window and pleads, "You can stop now! Can't you see you've already won?" incapable of predicting or comprehending your reply murmured between inhalations, "The reason ... I won ... is because ... I don't ... believe in finish lines."

RustCamp Reminiscences

On Saturday the first, I attended RustCamp, the first conference dedicated to the newish (in development for fiveish years, but having just hit version 1.0.0 this May, with all the stability guarantees that implies under the benevolent iron fist of semantic versioning) programming language Rust!


Why RustCamp? (It's a reasonable rhetorical question with which to begin this paragraph: going to a conference has opportunity costs in time and money; things worth blogging about are occasionally worth justifying—even if no one actually asked me for a justification.) A lot of the answer can be derived from the answer to a more fundamental question, "Why Rust?" And for me, I think a lot of the answer to that has to do with being sick of being a fake programmer living in a fake world that calls itself Python.

Don't get me wrong: Python is a very nice place to live: good weather, booming labor market, located in a good school district, with most of the books you might want already on the shelves of the main library and almost all of the others a mere hold request away. It's idyllic. Almost ... too idyllic, as if the trees and swimming pools and list comprehensions and strip malls are conspiring to hide something from us, to keep us from guessing what lurks in the underworld between the lines, the gears and gremlins feeding and turning in the layers of tools built on tools built on tools that undergird our experience. True, sometimes small imperfections in the underworld manifest themselves as strange happenings that we can't explain. But mostly, we don't worry ourselves about it. Life is simple in Python. We reassure our children that that legends of demon-king Malloc are just stories. Everything is a duck; ducks can have names and can be mutable or immutable. It all just works like you would expect from common sense, at least if you grew up around here.

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I used to think of $ in regular expressions as matching the end of the string. I was wrong! It actually might do something more subtle than that, depending on what regex engine you're using. In my native Python's re module, $

[m]atches the end of the string or just before the newline at the end of the string, and in MULTILINE mode also matches before a newline.

Note! The end of the string, or just before the newline at the end of the string.

In [2]: my_regex = re.compile("foo$")

In [3]: my_regex.match("foo")
Out[3]: <_sre.SRE_Match object; span=(0, 3), match='foo'>

In [4]: my_regex.match("foo\n")
Out[4]: <_sre.SRE_Match object; span=(0, 3), match='foo'>

I guess I can see the motivation—we often want to use the newline character as a terminator of lines (by definition) or files (by sacred tradition), without wanting to think of \n as really part of the content of interest—but the disjunctive behavior of $ can be a source of treacherous bugs in the fingers of misinformed programmers!

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The Second R

I want to code all of the things, but I also want to write at least some of the things, but sometimes putting things in words—simple things, things I know—can be hard. Every other day I dream of getting in some writing in the night after I return from the code mines across the bay, but the box where the writing tool lives is the same as the box where you can read everything that anyone else has ever written, and you can guess what I really do then, when it's easier to read than to farm, to eat than to write.

But writing is important, because we can imagine nearby possible worlds in which the distribution of verbal skills is incompetenceward of our own, and the people in those worlds are sadder and poorer than us, the clumsiness of their attempts at communication leaving them less effective at coordinating their activities to dominate nature: colleagues maneuver against each other, ineffectually; television is less interesting; lovers stare into each others' eyes having less idea than you of what they're really looking at.

And in our own world, where people can say more, but not enough—I can read, but I'm missing something ... I can reckon with 'rithmetic, which serves a purpose, but cannot in human terms express the richness of vision that courses through ... something. And it cannot be a part of inner peace and glory until paired with something that does, high though the price may be for that something!

The second R, which is yet not an R. I want this more than I can say.


Sometimes I worry that people with power in Society will look down on me for my pronunciation of the .pyc extension for Python bytecode files. I always want to say pike-cee, even though many would argue that the c should either be hard (pike) or said as the name of the letter (py-cee), but certainly not both in sequence!


(8:5x a.m., an office on the someteenth floor of the twenty-somethingth tallest building in San Francisco)

"Good morning!"


"How was your weekend? Did you do anything exciting? Maybe you went to a movie, or to the beach—"


"Or embarked on some heroic endeavor of engineering, the likes of which threaten to upend our understanding of the nature of computation itself?"

"No, nothing like that," (sighing, resignedly) "how was your weekend?"

(pretending to inspect his or her fingernails) "My weekend? Oh, nothing special—hung out, did some grocery shopping—"

"Uh huh."

"—wrote a compiler—"

The Foundations of Erasure Codes

(cross-posted from the SwiftStack Blog)

In enabling mechanism to combine together general symbols, in successions of unlimited variety and extent, a uniting link is established between the operations of matter and the abstract mental processes of the most abstract branch of mathematical science. A new, a vast, and a powerful language is developed for the future use of analysis, in which to wield its truths so that these may become of more speedy and accurate practical application for the purposes of mankind [sic] than the means hitherto in our possession have rendered possible.

Ada Lovelace on Charles Babbage's Analytical Engine, 1842

Dear reader, if you're reading [the SwiftStack Blog], you may have already heard that erasure codes have been added to OpenStack Swift (in beta for the 2.3.0 Kilo release, with continuing improvements thereafter) and that this is a really great thing that will make the world a better place.

All of this is entirely true. But what is perhaps less widely heard is exactly what erasure codes are and exactly why their arrival in Swift is a really great thing that will make the world a better place. That is what I aim to show you in this post—and I do mean show, not merely tell, for while integrating erasure codes into a production-grade storage system is (was!) an immense effort requiring months of work by some of the finest programmers the human race has to offer, the core idea is actually simple enough to fit in a (longish) blog post. Indeed, by the end of this post, we will have written a complete working implementation of a simple variant of Reed–Solomon coding, not entirely unlike what is used in Swift itself. No prior knowledge will be assumed except a working knowledge of high-school algebra and the Python programming language.

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