Programming

The earliest memory I have of ‘programming’ is in the early/mid 90s when my father brought home a computer from work. We could play games on it … so of course I took the spreadsheet program he used (LOTUS 123, did I date myself with that?) and tried to modify it to print out a helpful message for him. It … halfway worked? At least I could undo it so he could get back to work…

After that, I picked up programming for real in QBASIC (I still have a few of those programs lying around), got my own (junky) Linux desktop from my cousin, tried to learn VBasic (without a Windows machine), and eventually made it to high school… In college, I studied computer science and mathematics, mostly programming in Java/.NET, although with a bit of everything in the mix. A few of my oldest programming posts on this blog are from that time.

After that, on to grad school! Originally, I was going to study computational linguistics, but that fell through. Then programming languages (the school’s specialty). And finally I ended up studying censorship and computer security… before taking a hard turn into the private sector to follow my PhD advisor.

Since then, I’ve worked in the computer security space at a couple of different companies. Some don’t exist any more, some you’ve probably heard of. I still program for fun too, and not just in security.

But really, I still have a habit of doing a little bit of everything. Whatever seems interesting at the time!

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Tiny Helper Scripts for Command Line MySQL

2019-04-27

Quite often, I’ll find myself wanting to query and manipulate MySQL data entirely on the command line. I could be building up a pipeline or working on a task that I’m going to eventually automate but haven’t quite gotten to yet. Whenver I have to do something like that, I have a small pile of scripts I’ve written over time that help out:

  • skiphead: Skip the first line of output, used to skip over headers in a query response
  • skipuntil: Skip all lines until we see one matching a pattern, used to resume partial tasks
  • commaify: Take a list of single values on the command line and turn them into a comma separated list (for use in IN clauses)
  • csv2json: a previously posted script for converting csv/tab delimited output to json
  • jq: not my script, but used to take the output of csv2json and query it further in ways that would be complicated to do with SQL

Admitedly, the first two of those are one liners and I could easily remember them, but the advantage of a single command that does it is tab completion. sk<tab>, arrow to select which one I want, and off we go. I could put them as an alias, but I don’t always use the same shell (mostly fish, but sometimes Bash or Zsh).

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Listing and Downloading S3 Versions

2019-01-04

Today I found the need to look through all old versions of a file in S3 that had versioning turned on. You can do it through the AWS Console, but I prefer command line tools. You can do it with awscli, but the flags are long and I can never quite remember them. So let’s write up a quick script using boto3 (and as a bonus, try out click)!

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AoC 2018 Day 14: Functionally Circular Elfs

2018-12-14

Source: Chocolate Charts

Part 1: Create an infinite stream of numbers, by starting with [3, 7] with two pointers: 0 and 1. To add values to the list:

  • Add the current values of the two pointers
    • If the value is less than ten, add that value to the end of the list
    • If the value is greater or equal to ten, add 1 and then the ones digits to the end of the list
  • Update each pointer by adding the value it is pointing at to its current index plus one

With that algorithm, find the ten digits after a given index.

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AoC 2018 Day 13: Mine Cart Madness

2018-12-13

Source: Mine Cart Madness

Part 1: Load a minecart track that looks like this:

/->-\
| | /—-
| /-+–+-\ | | | | | v | -+-/ -+–/ -—–/


> Assuming minecarts follow the tracks and alternate turning left, going straight, and turning right on each intersection (`+`), where does the first collision occur?

> NOTE: Update carts top to bottom, left to right. Carts can collide mid update.





Okay. It's an interesting data format problem mostly. And we have to deal a bit with not being imperative, in particular when we're doing the updates, since having collisions happen halfway through an update is not so great. Let's load it:

```racket
(struct point (x y) #:transparent)
(struct cart (location velocity next-turn) #:transparent)
(struct track (data carts top-left bottom-right) #:transparent)

The goal will be to load the tracks into a hash of point to character (so I know how the track turns / intersects) and separately store the carts. I’ll want to process the track after the initial load to replace carts with their underlying track and get the initial velocity as well. Finally, next-turn will always start as 'left, but we’ll deal with that later.

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AoC 2018 Day 9: Marble Madness

2018-12-09

Source: Marble Mania

Part 1: Place marbles in a circle such that each marble is placed by skipping one place except for marbles divisible by 23. For those, don’t place them, skip back 7 places, and remove that marble as well. Add these two marbles to your current score.

Given a specific player count and last marble, what’s the highest score?

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