January 1, 2018

things you don't learn in grad school

oncall exists.
the data is never available how you need it.
unit tests matter.
pushing code after 3pm is risky if you’re not willing to work all night. (courtesy Paul Joos)

November 29, 2017

url encoding safe relational operators

I was catching up on Jesse Wilson’s blog this morning, and in particular his post URL Encoding Is Material. In that article, he says

My advice

If you’re defining your own URLs, you’ll save a lot of trouble by avoiding characters like <, >, {, }, +, ^, &, |, and ;.

I came across this problem in one of my projects at work: I wanted a page to display some recent records with 1) a name field provided by the user and 2) a value field that match $l \leq \text{value} \leq b$, where $l$ and $b$ are given by the user. I also wanted that page to have a URL representing that condition, so that it could be easily shared with teammates and soforth. When I started working on it, I didn’t have Jesse’s wisdom, and so I naively came up with a URL structure something like

November 13, 2017

snack buying

I got this text message from my father-in-law:

Ok. Soda 1.50 Chocolate bar 1.00 Gum 0.10 Jelly Bean .05

Have to buy exactly 14 items and spend $10

At least one of each.

There are 4 diff combos. (Order: soda, chocolate, gum and jelly bean)

Got 5-2-3-4 3-5-4-2

Can’t get others. Any ideas? :)

I whipped up this solution to check in python:

#!/usr/bin/python3
# created_at: 2017-11-13 13:53:19 -0800

def main():
    solutions = 0
    for si in range(1,7):
        for ci in range(1,11):
            for gi in range(1,101):
                for ji in range(1,201):
                    total = si*150 + ci*100 + gi*10 + ji*5
                    items = si + ci + gi + ji
                    if total == 1000 and items == 14:
                        print(si,ci,gi,ji, total, items)
                        solutions += 1
    print(solutions)

if __name__ == "__main__":
    main()

The core of this solution is the check

November 7, 2017

even the ceo doesn't get an office

Square is a fantastic place to work, and has been for my entire time here. One thing I’m not such a fan of, though, is the open office layout we have – and share with many other startups.

Somehow I have the distinct memory of thinking, “Wow, even the CEO doesn’t get an office here! That’s really cool!” I had an important realization today, though. It’s not that the CEO of companies with open offices don’t get an office – it’s that they don’t want one.

October 27, 2017

500 Million Dollars!

I watched Destin’s $500 Million Dollars video:

and had a few thoughts:

my highschool CS education

My highschool had computer teachers, but no computer science teachers. Luckily, we did have a teacher (Dick Van Kirk!) that was willing to sponsor an independent study of some computer science topics. I read the AP Computer Science A study guides and a bunch of the Java: How to Program (Deitel & Deitel) book and managed to get through the AP test with a top score. This enabled me to skip over the intro CSE142 at University of Washington.

September 12, 2017

confident women are getting bypassed by overconfident men

Really interesting youtube talk: confident women are getting bypassed by overconfident men

August 31, 2017

python attrs

I came across a very interesting library in a HN thread: the python attrs library.

In particular, this seems like a great way to do the “dumb data objects” they talk about in the end of object inheritance, and also related to (but maybe lighter weight than) zope.interface.

This also seems very similar to what I use autovalue for at work.

One particularly interesting application is a “code database” – using static, checked-in-to-version-control definitions of some data model as a sort of very-fast-to-read, very-slow-to-update “Data Model”. I find this fascinating: Code shares a lot of properties with great data stores: ability to rollback (git revert) and accountability/auditability (git blame). It also makes a lot of fairly hard problems much simpler: you don’t need to poll the database for changes. You don’t need to invalidate any caches. You don’t need to consider a “split brain” environment where half of the in-memory caches have updated but the other half haven’t. You don’t need to consider failure cases of how long the in-memory cache is allowed to be invalid: you just fail to boot up on deploy. (Admittedly, there’s still an opportunity window for split brain behavior for the duration of the deploy, but this is a lot easier to reason about than an essentially arbitrary.)

July 17, 2017

klr650 planned upgrades

I’m planning on “civilizing” my KLR650 just a tiny bit, since it is coming up on 1500 miles and I haven’t made it offroad at all yet.

There are two (fairly minor) issues with the stock setup, as far as I’m currently concerned:

First, I’d prefer the gearing to be just a little bit taller so I don’t have to wind it up quite as much. The engine just runs a little faster than I’d like at freeway speeds, and even driving around town it just feels slightly off. So I’m thinking about swapping out the stock 15T countershaft sprocket for a 16T. That changes the final drive from 2.87 to 2.69, and saves about 400 RPM at freeway speed, which doesn’t sound like much, but should quiet it up nicely. I found a website called gearingcommander that allows all of these calculations pretty nicely.

May 5, 2017

relational java explorations with sqlite3 vtab

One idea i have been mulling over lately is exposing a java codebase relationally, with queries like:

SELECT *
FROM classes c
JOIN annotations a
  ON a.class_id = c.id
WHERE a.name = 'MyAnnotationClass';

The idea here is that you could search a codebase by pretending that you had tables for a whole bunch of things like:

classes
annotations
variables
literals
methods

This would be a useful thing because instead of relying on an IDE like IntelliJ to do “find usages” operations, you could actually script those interactions. Admittedly, of course, Java has some pretty sophisticated reflection APIs to find this sort of stuff too, but it seems like exploring the structure could be much easier writing Java code to traverse those trees.

April 19, 2017

toy/life data models

I’ve been experimenting a lot with some kinda “toy” data models based on random things that I wish there was a database to query, but isn’t. For example:

What was my average arrival time this week?
How much of my equity has vested before a certain date?
When was the last time we had spaghetti for dinner?

I’ve been doing this with flat JSON files. This is a bit of an odd choice for me; I actually love schematizing data models in protobuf and MySQL and designing proper indices for the data models I work on during work hours.