Blog: #learning-elixir

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.

Recursion

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.

Processes

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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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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