AoC 2021 Day 10: Chunkinator

Source: Syntax Scoring

Part 1: Given a sequence of () [] {}, and <> with nesting allowed. Find the first syntax error (where the wrong closing symbol is used). Scoring 3, 57, 1197, and 25137 respectively for each error, calculate the total error score.


AoC 2017 Day 9: Garbage Gobbler

Source: Stream Processing

Part 1: An input stream can contain:

  • groups are delimited by { and }, groups are nestable and may contain garbage or data (objects within a group are comma delimited)
  • garbage is delimited by < and >, groups cannot be nested within garbage, a ! within garbage is an escape character: !> does not end a garbage segment

The score of a single group is equal to how many times it is nested (the innermost group of {{{}}} has score 3).

The score of a stream is the sum of the scores of all groups in that stream.

What is the total score of your input?


Making music, part 3: Making noise

Last week we parsed some music. That post was in a bit of a hurry, so we had to leave off a fair few important pieces (like ties and slurs for one; chords for a rather bigger one). We’ll get to them soon, but for now we want to actually get something playing back.


Making music, part 2: Taking shape

It’s been a bit, but as you may have noticed life is a bit mad at the moment. But I’ve still made some progress.

When we left off last time, we’d finished the first step towards making some lovely music with Racket: tokenization. Now we want to take those songs and form them into something actually approaching music.


Making music, part 1: Reading ABC notation

It’s been a bit since I’ve had time to post1, but I’ve got an interesting new project that I’ve been working on. It’s a bit more complicated, ergo spread out over a few posts, but those tend to be the more interesting posts anyway, eh?

The basic idea is that I want to be able to write and play music in Racket. One end goal would be to make a library available for the C211 class to give them something else to work with (in addition to <a href="//"/wombat-ide/c211-image-api/">images and <a href="//"/wombat-ide/c211-turtle-api/">turtles). To that end, here’s my current plan of attack2:

  • Write a lexer for ABC notation to turn raw text into a list of tokens
  • Write a parser to turn those tokens into a song (for example dealing with the interactions between key signature/accidentals and meter/note duration)
  • Use the rsound library on Planet2 / pkg to play back individuals notes and chords
  • Tie it all together to play a parsed song in ABC notation using the rsound library
  • (maybe): Use the rsound library to save ABC files as WAV audio
  • (maybe): Figure out the format and save ABC files as MIDI
  • (maybe): Render songs as music sheets/li>

Sounds like fun! Let’s get started.