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Learning Elixir, part 2

Continuing on with working my way through the Elixir introduction. I’m trying to figure out how to keep this from taking forever (especially since I’m only doing this in little bits of free time here and there), so there’ll be a bit less commentary than last time.

Binaries, strings, and charlists

I love that you can use ? to show the code point in front of a character literal. (Not that ord("a") or "a".charCodeAt(0) is all that harder.)

Pattern matching on binaries and bitstrings is good.

Keyword lists and maps

I like being able to use atoms as the keys in keyword lists and maps. It’s a small thing, but it’s nice.

Ooh, do-blocks are just syntactic sugar. (Apparently I really like it when control flow statements are just special syntax on top of lower-level constructs like keyword lists.)

Modules and functions

Okay, like in Rust, modules are named in code (with defmodule) rather than named implicitly by whatever the containing file is called. I think I like that it’s explicit.

I don’t think I’ve seen private functions specified by changing the function definition keyword (def to defp in this case). Usually what I’ve seen is a separate keyword (private) or private-by-default (Rust) or capitalization change (Go) or mere convention with underscores (Python). Cool.

Ooh, guards on function definitions. I like this. Function overloading++. (Har har.) I know you can get the same behavior with conditional statements in a single function body, and that’s probably less verbose, but still. This seems easier to reason about.

Function capturing is interesting. I guess it’s needed because the parentheses in function calls are optional.

Default arguments with \\. Huh. Moving things up to a function head if there’s more than one default argument is also interesting. Brings back the old C/C++ days with header files.


Guards on function definitions: great for recursion. I like being able to separate out the base/termination case like that.

I think multiple function clauses might be clearer than Enum.reduce for writing reduce algorithms. (Though I do like having the function at the end with Enum.reduce — in JavaScript, it feels like the initial value is often harder to see when it’s at the end after the function body.)

Enumerables and streams

Being able to map/reduce on ranges is nice and is something I wish more languages had. (I’ve had to do this in JavaScript a couple times recently.)

The famed pipe operator at last! Looking forward to using it in practice, since it does seem like it makes chains of function calls easier to understand.

Streams look nice.


Okay, so these are kind of like lightweight threads, similar to goroutines in Go. That makes more sense (referencing my questions in the last post). I like the send/receive syntax a bit more than Go’s channel syntax, too.

Ooh, the after timeout! I really like that that’s built in.

The docs on linked processes make it sound like you build your own supervisors in Elixir, which sounds amazing. Can’t wait to learn more about that. (I’ve always used external processes like supervisord.)

This bit about sending messages to and from processes being the normal way to maintain application state? That’s really intriguing — something I haven’t really seen before. (At least not from the perspective of being built in to the language.) Looking forward to seeing what this looks like in practice.

IO and the file system

The names of File.cp_r/2 and File.rm_rf/1 make me irrationally happy. Especially given the danger of the latter. Ha.

Oh interesting, files are processes under the hood. Beginning to suspect this may be an everything-is-a-process type language. Which is new to me and very interesting.

Okay, we’ll stop there for now. Halfway through the introduction!

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Thoughts on a little language for generative art

I’ve been thinking about resurrecting the Marks idea, partly because I’d like to use it for my art and partly because I want to have my 12in23 project (for at least some of the languages) be a simplified Marks parser. (And a little bit because my dad’s name was Mark.)

As a refresher: Marks is going to be a DSL for generative art. In its newest incarnation, it could also be used more generally for composition, but generative art is the focus.

The current plan is to have a number of types of top-level blocks: layers, brushes, path profiles, color definitions, functions, and properties, and probably a few others I haven’t fully thought through yet. A rough draft, which still needs a lot of refining, and which doesn’t yet include a lot of the ideas I’ll include in the notes below:

size 7500x7500
background white
color black #000
color red hsl(0 50% 50%)
seed 24601

brush circles {
  random.xy0(num: 50).each {
    circle(x, y, r: random(0.1), fill: black)

pathprofile mytaper {

layer.svg some shapes {
  subtract {
    circle(x: $width/2, y: $height/2, r: $height/2*.8, fill: red)
    rectangle(x: random.x, y: random.y, w: random($width - $x), h: 50, fill: red.lighten(0.2))
  mask {
    line(x1: random.x, y1: random.y, x2: random.x, y2: random.y, strokeWidth: random(5, 20), brush: circles)
  blend soft-light

layer.raster noise {
  xy.each {
    red.jitter(hue: 0.2)
  blend soft-light
  opacity 0.2

Notes, acknowledging that this is mostly brainstorming and not a final, consolidated list:

  • Layers are the fundamental block, in that nothing gets output if there aren’t any layers.
  • Layers can be SVG (which then gets rendered to raster once the layer is done) or raster.
  • The background property adds a bottom layer filled with the color (leaving it out allows for transparency).
  • There’s a debug flag that exports each layer to a file individually (minus blending mode and opacity), so you can see what happened.
  • SVG layer commands include CSG booleans.
  • The “some shapes” and “noise” bits on the layers are layer names.
  • This isn’t shown here, but layers can be different sizes and can be positioned.
  • I’m leaning towards having Marks be as purely declarative as possible, though I suspect I’ll still need some imperative support (a random walk, for example, would be more difficult to do declaratively) (though I’m still going to see if I can make it work somehow). I’m thinking the top-level function blocks would be where imperative code happens, maybe.
  • random.x would get a random X coordinate within the canvas.
  • Layers can be masked, and within the mask there can be any rendering commands (still working on nomenclature here) that are available for the current layer type (which mostly means raster commands aren’t available on SVG layers except in places where an image is expected).
  • For SVG layers, the layer blending mode and opacity only apply after rasterization.
  • The xy variable returns an array of all the coordinates of the rasterized canvas.
  • Numbers and colors have a jitter method that allows for jittering within a set range .
  • The brush block allows using rendering commands to create a brush that can then be used to stroke paths or fill shapes.
  • The pathprofile block needs (a lot of) work, but the idea is to have some way to describe the profile of a path, so you can have paths with the width varying along the stroke. Ideally, this would support both relative percentage-based profiles (leading to different effects for short paths vs. long paths) and absolute profiles (so the effect is the same for any length of path that matches the values) and possibly a mix of both (absolute for the first 50px and then relatively fade out for the rest, however long that is, for example).
  • Good support for path navigation and manipulation. Be able to easily work with points every 20px along the path, for example, or every control point, or fifty random points along the path. Also be able to get normals and tangents for any points along the path.
  • Importing images from disk will of course be included.
  • This is a lower priority for me: animation support. There would be access to a frame variable. Each frame could use the same global random seed (with each layer getting seeded individually to try to preserve behavior) or could use a different seed.
  • This is moving more into pie in the sky territory, but I’ve become enamored of the idea of having Marks support 3D, including programmatic generation of the canvas texture in 3D and being able to layer paint (and then scrape some off to see layers underneath) and get impasto effects and all that. This would also support moving the camera around and creating/modifying 3D models to some extent. I like this a lot and I think it fits conceptually, but it may be a bit Too Much. (Part of me thinks it would make far more sense to do this separately as something in Blender, where you get so many 3D features for free.)
  • Marks files can import other Marks files.
  • Custom fill functions can be written, where you provide some code that then generates the content for whatever polygon is filled (clipped to the polygon boundary).
  • Shape packing helpers are planned, too, so you can fill a polygon with circles or any other shape. I’d like this to be programmatic, so that each shape could be different.
  • Layer filters will be included, too — blur, threshold, erosion/dilation, etc. — and these will apply to masks as well.
  • Colors can be defined in the usual formats (HSL, RGB, hex) and also LCH, and they can be modified dynamically (lightened, darkened, etc.).

There will undoubtedly be simplification along the way, since this is…a lot. The initial core implementation would (in my mind) be layers (both SVG and render, with a basic set of commands, excluding masks but including blending modes and opacity), colors, the random generator, debug mode, and exporting a final image. That’s enough base functionality for it to be usable.

I’m going to be working on a BNF grammar for this soon, once I get the syntax finalized enough that writing a parser is feasible.

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Learning Elixir, part 1

As my first 12in23 language, here’s my initial foray into learning Elixir. These notes will be informal and more stream of consciousness than anything. I have no idea if anyone will get any benefit from reading this, but I’m sure going to have fun writing it.

I’m starting out by working my way through the Elixir introduction. Once I finish that, I’ll start on a real project.

Basic types

Interesting that string concatenation is <> (which I’m used to meaning != in SQL and Excel/Google Sheets).

The naming of the div and rem functions makes sense. It also amuses me from an HTML/CSS perspective. (You could pull <> into this as well.)

Being able to drop the parentheses in function calls is nice (in that it’s cleaner), but I think the legibility gain from including them is probably worth it.

Ah, I think I’ve seen this kind of function identification (name + arity) somewhere before (maybe Haskell?). It’s a little different and reminds me vaguely of man pages, but I like it — nice to be able to tell at a glance how many arguments a function takes.

The built-in help in iex seems nice, and I’m liking the arity identification more and more as I continue to see it. Looking through the h/0 list now for a brief detour. Interesting that you can compile a file and export bytecode from the REPL. And hot dang, introspection with i is great. I don’t know what PIDs and ports are (in context of Elixir, that is). Okay, from the processes page it looks like PIDs are related to processes which are a fundamental Elixir concept — and not the same as OS processes. Also looks this processes page is a later section of the introduction, so I’ll set it aside for now. (At this point, I’m curious as to why you can set PIDs from strings or atoms or three integers, as opposed to having the system auto-assign them. Also intrigued by ports and references — in the languages I’ve used, ports are almost always ints.)

It’s been a while since I used a language with atoms (Ruby). Intrigued by aliases, looking forward to learning more about them later.

Nice to see string interpolation works as expected. (And in another brief detour I’m now wondering about the different syntaxes across languages. I’ve seen `${...}` in JavaScript and f"{...}" in Python. The "#{...}" here is interesting.) One thing I’m noticing is that there doesn’t seem to be an uninterpolated string. (Both JS and Python have those.) I wonder how much of a performance hit there is in Elixir from having all strings support interpolation. Probably not enough to matter most of the time.

Up next: anonymous functions. The fn and end feel a little noisy syntactically, but with syntax highlighting it’s probably fine. Interesting that invocation needs the . before the parentheses — so variables and functions appear to be in separate namespaces. I wonder if that’s actually true, and if there are other namespaces as well. Glad to see closures. (It would be weird not to, to be honest.)

Ah, list concatenation with ++ and --. One of the reasons I think it’s good to have broad experience with programming languages, by the way, is so your brain can fill up with multiple meanings for almost every symbol. I jest.

Interesting that a list of ASCII numbers automatically returns a charlist. And interesting that charlists are not strings. (Maybe this is the answer to the earlier comment about all strings being interpolated. I wonder if charlists are limited to ASCII.)

I’m realizing that this is going to take forever if I keep commenting on every last little thing. Attempting now to be more selective with comments.

Okay, lists and tuples. At this point I’m wondering if there are structs/records/objects/etc. Update: I did a quick look ahead and yes, there are maps and structs.

I like that the names for size and linear tell you if the operation is O(1) or O(n).

Basic operators

Ooh, the distinction between or/and/not and ||/&&/! is interesting. And here’s === again. Looks like it’s not quite the same as in JavaScript but is conceptually similar (stricter than ==).

Cross-data-type sorting is interesting.

Pattern matching

Ah, I love pattern matching. (I’ve mostly seen it in Rust so far.)

Good to see tuple and list destructuring. And I like how you can match as part of the destructuring. I don’t think I’ve seen that before. (But it’s been a little while since I’ve used Rust — you could say I’m getting rusty (I am so sorry) — and I can’t remember if it has this.)

Ooh, I like the [head | tail] matching. That’s cool.

The pin operator is new (to me) and interesting. Kind of a different way of doing immutability. And in matching, I like how it lets you use a variable without having to overwrite what’s in the variable (which would happen without pinning). I’m also thinking about how it’s the same operator for pinning version numbers in npm.

case, cond, and if

I like case. And guards. (Guards in Elixir, I mean. I’m not making a statement about guards out in the real world.)

Oh, now that’s interesting — anonymous functions can have multiple clauses (which I think I’ve seen in Haskell) but they can also have guards. That seems like a potentially cleaner way to handle main branches of logic within a function, maybe, but I don’t know — food for thought. And interesting that it’s restricted by arity, though in Elixir it appears that functions with different arity are considered different functions entirely. (Which is quite different from variadic functions in, say, JavaScript or Python.)

cond feels (to a degree) like a more powerful switch. Except in this case you can change the condition (both left- and right-hand sides!) for each branch. That’s intriguing. (Actually, giving it a few seconds’ more thought, case is much closer to a switch than cond is. Both of them are more flexible, though.) Playing around with cond feels kind of like having a superpower.

Happy to see unless. I haven’t used an unless since Perl a long, long time ago. I know it’s just syntactic sugar but I like it.

I love that if can return a value (as in Rust). It’s something I often find myself missing when I’m writing, say, JavaScript. Ternaries are the next best thing but not as ideal, in my opinion.

Okay, this is long enough for today. Looking forward to continuing through the tutorial soon! I’m really enjoying this.

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I heard about Exercism’s 12in23 challenge and while I don’t care much about doing the official challenge, I do like the idea of learning more programming languages this year. (And every year, for that matter.)

As boring backstory, here’s a quick list of languages I’ve already written projects in and which therefore won’t be eligible. In very rough chronological order: BASIC (BASICA, GW-BASIC, QBasic), Pascal, C, C++, ASP.NET, VB.NET, PHP, Perl, Ruby, Python, JavaScript, Objective-C, MSP430 assembly, Java, GLSL, Go, and Rust. We’re also starting to use TypeScript at work, so I’m going to leave it out.

The languages I want to learn this year, in no particular order: Elixir, Zig, Haskell, Lisp, Clojure, Unison, COBOL, FORTRAN, WebAssembly text format, OCaml, Nim, 6502 assembly, Scala, and D. This list is subject to change.

I’ve read about some of these, and several years ago I taught some short intros on Haskell and Lisp for coworkers (which just entailed walking through the basic features of each language, nothing fancy), but I haven’t written any actual projects in any of them. That’s going to be my main focus this time, by the way: writing something real in each language. Probably a parser. We’ll see. (I also haven’t decided whether I’ll do the same project in each language.) And I’ll be blogging about each language as I learn it.

First up: Elixir. Several years ago I read a little bit about Erlang and the BEAM, and I’ve looked at the Elixir intro page two or three times, but I haven’t really read anything in detail. I know that Phoenix is a web framework, and PETAL is the new LAMP (in some circles, anyway), and LiveView is apparently amazing, but that’s about it. Here we go!

(I’m going to use the #12in23 tag for these posts, by the way, so that I don’t have to think of a new tag name.)

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