List append (++) does not return a list

What you’re seeing are charlists using the ~c sigil. They are the exact data you expected, but printed as text to allow interoperability with erlang, which uses charlists as their default string type: List — Elixir v1.20.2

I suspected that this may be something like that. Is there a way of ‘forcing’ a standard list view in the console?
I assume that this will make no difference for the program (ie. I can pass the list to another function and it will work).

The link I posted shows how to configure the inspect protocol that way. IEx.configure can be used to configure iex with custom inspect options. Indeed the application itself doesn’t care. This is just something relevant to printing the data for human consumption.

Thanks.

IEx.configure(inspect: [charlists: :as_lists])

Run this manually inside iex or put it in a file called .iex.exs at the root of your project and it will be ran automatically on iex startup in that directory.

As an aside, I completely forgot this was out here…

Which, naturally, includes this very issue. I’m guessing this post is not very visible and only appears in searches… which in a case like this is more likely to not appear in a search since you’d kinda got to know what the issue was in the first place to hit the right search terms for it.

It’s a good idea… but I wonder if there’s a way to call this out for special attention so that it isn’t forgettable for those that might add to it or discoverable for those that might need it.

Cool, TIL. But this just flips the confusion the other way around, no?

Erlang/OTP 25 [erts-13.2.2.7] [source] [64-bit] [smp:20:20] [ds:20:20:10] [async-threads:1] [jit:ns]

Interactive Elixir (1.15.7) - press Ctrl+C to exit (type h() ENTER for help)
iex(1)> [97, 98, 99]                                  
~c"abc"
iex(2)> ~c"abc"
~c"abc"
iex(3)> IEx.configure(inspect: [charlists: :as_lists])
:ok
iex(4)> [97, 98, 99]                                  
[97, 98, 99]
iex(5)> ~c"abc"                                       
[97, 98, 99]

I’m guessing the tradeoff is that one is less likely to find themself surprised when a charlist is represented as a list of integers, compared to the more-common case where a list of integers is rendered as a charlist, which is a very common surprise for beginners. I suppose that if you’re deliberately working with charlists, you’re probably deep enough into the Elixir rabbit-hole to understand what is happening behind the scenes.

To confirm my obvious suspicion, the behaviour can be reverted to the default with this line:

IEx.configure(inspect: [charlists: :as_charlists])

Thanks again for another excellent tip. I’m gonna dogfood this one for a bit…

Yes, I am guessing the same. I don’t like the status quo either but unless we’re willing to go contribute to OTP itself (or maybe only to Elixir? not sure actually) then it’s going to stay that way and we should make the crutches obvious. At least they restore things to a bit saner state (hopefully).

Hey, I’m in no position to complain while I’m standing on the shoulders of giants. But I have not encountered this tip before, and I think it is definitely worth knowing.

It’s funny too, because it’s one of those things that’s obvious in retrospect. I’ve used a line like that to temporarily change the charlist rendering style. I just never though to put it in my IEx config.

I agree. It’s not obvious. I’d even argue this config should be the default; I really don’t see who would derive an actual tangible value out of seeing some integer lists as charlists.