Two years ago, I did part of Advent of Code 2020 using the Rust language. It was a lot of fun, so let’s try it again!

The problem statement

Our input looks something like this:

1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

Each group of lines separated by an empty line is a list of food items an elf is carrying: each line corresponds to the number of calories in that food.

My honeymoon with the Go language is extremely over.

This article is going to have a different tone from what I’ve been posting the past year - it’s a proper rant. And I always feel bad writing those, because, inevitably, it discusses things a lot of people have been working very hard on.

In spite of that, here we are.

Having invested thousands of hours into the language, and implemented several critical (to my employer) pieces of infrastructure with it, I wish I hadn’t.

In the two years since I’ve posted I want off Mr Golang’s Wild Ride, it’s made the rounds time and time again, on Reddit, on Lobste.rs, on HackerNews, and elsewhere.

And every time, it elicits the same responses:

• You talk about Windows: that’s not what Go is good at! (Also, who cares?)
• This is very one-sided: you’re not talking about the good sides of Go!

Another day, another problem.

This time the problem looks suspiciously like Conway’s Game of Life, or, I guess, any old Cellular automaton.

We have a map like so:

L.LL.LL.LL LLLLLLL.LL L.L.L..L.. LLLL.LL.LL L.LL.LL.LL L.LLLLL.LL ..L.L..... LLLLLLLLLL L.LLLLLL.L L.LLLLL.LL

And for each iteration:

• L symbols turn into # if there’s no # in any of the 8 adjacent cells

In my previous article, I said I needed to stop thinking of Rust generics as Java generics, because in Rust, generic types are erased.

Someone gently pointed out that they are also erased in Java, the difference was elsewhere. And so, let’s learn the difference together.

Java generics

I learned Java first (a long, long time ago), and their approach to generics made sense to me at the time.

Time for the Day 12 problem!

In this problem, we have a ship. And we have navigation instructions:

• Action N means to move north by the given value.
• Action S means to move south by the given value.
• Action E means to move east by the given value.
• Action W means to move west by the given value.
• Action L means to turn left the given number of degrees.
• Action R means to turn right the given number of degrees.

Our catscii program does everything we want it to do, except that it’s a command-line application rather than a web server. Let’s fix that.

Enter axum

The documentation for the axum crate tells us how to make a basic web server, and we honestly don’t need much more than that.

So let’s add axum:

amos@miles:~/catscii$ cargo add axum@0.6 Updating crates.io index Adding axum =0.6 to dependencies. Features: + form + http1 + json + matched-path + original-uri + query + tokio + tower-log - __private_docs - headers - http2 - macros - multipart - w

Advent of Code gets harder and harder, and I’m not getting any smarter. Or any more free time. So, in order to close out this series anyway, I’m going to try and port other people’s solutions from “language X” to Rust. That way, they already figured out the hard stuff, and we can just focus on the Rust bits!

Sounds good? Good. Let’s proceed.

In the day 8 problem, our input is a height map:

30373 25512 65332 33549 35390

This is a 5x5 grid, and every number denotes the height of a tree. For part 1, we must find out how many trees are visible from the outside of the grid.

If we consider the first row, from the left: only the 3 is visible: it obscures the 0. From the right, 3 and 7 are visible.

The year is drawing to a close, and I’m going off on a much-needed holiday next week. This seems like a good time to look back at the past twelve months!

I can’t believe that shipped

2018 was the year of foundational work. As far as “work work” is concerned, I spent the first 9 months finishing up my largest project ever, the itch v25 rewrite.