Copper – A minimal low-level programming language with OOP and generics (tibleiz.net)

155 points by bogdanoff_2 •

Not mine, but I found this to be really interesting as a language created by one person for their own use.

Also really interesting are the author's blog with articles on language design (for example his thoughts on exceptions, and how he added them to his language, then decided against them), and the change log for the language, showing its evolution.

https://tibleiz.net/

https://tibleiz.net/copper/changes.html

It’s similar to Python syntax.

From the website itself:

> Ruby-style syntax

Also, Python has significant whitespace, which this language does not appear to have.

The end syntax is definitely Ruby-style, but I guess I felt that way just from looking at syntax like var, func, and for x in. It does seem like a mix of the two, but maybe it’s because I’m so used to Python that I noticed the Python-like syntax first. Thanks for pointing that out.

Glad they chose the more sane way of Ruby, regarding whitespace.

Garbage collected? Couldn’t tell from the docs.

I thought it would be because it looks so Python/Ruby-like, but in the source I don't see anything related to a GC at a glance and it has an allocator interface: https://tibleiz.net/browser.html?path=std&title=Standard%20L... (click on "memory" then "memory-allocator.co")

It seems pretty tasteful, but I don't see anything about character sets. How does it support Unicode? What does a string of 16-bit characters represent?

There do seem to be some Unicode constants in the standard library:

https://tibleiz.net/browser.html?path=std&title=Standard%20L...

Looks like Crystal to me. But with stronger typing.

https://crystal-lang.org

Neat little language...

Stronger how?

Definitely more explicit by default though.

But yes, very neat. I'd miss Enumerable though, if they manage to get that to play with manual allocation that would be even neater.

This might be my new favorite language. Deeply sane.

Exactly

Seems like Dart with indentation instead of braces.

It doesn’t look like it cares about indentation. It’s more like Basic or Ruby.

The simplicity is appreciated.

I need to put a disclaimer to say that I hate when people hijack a post about foo to talk about bar, but:

> The language is not object oriented but it provides some features to facilitate object oriented designs.

It has classes and implicit `self`. Not nothing, but I don't think it's incorrect to say has any more OOP than general purpose languages like Lua or JavaScript in that sense.

Something like Pony[1] is a more mature and feature rich entry and has a much better OOP story.

All that said: a) I'm sorry for doing the thing I hate when other people do

b) Creating a language is a big undertaking, and it's super cool that they did it

c) I see it seems to already be written in Copper too, which is also very neat!

[1]: https://www.ponylang.io/

Since we’re nitpicking: you used a double negative, which is a confusing way of communicating an idea.

The bike shedders have entered the chat.

There's a difference between nitpicking the topic of the article and nitpicking someone's grammar.

To be fair, it really is a confusing way of communicating, and it’s useful feedback when taken to heart.

It's not confusing.

> Not nothing, but I don't think it's incorrect to say has any more OOP than general purpose languages like Lua or JavaScript in that sense.

IMO, that text is confusing.

“Not nothing” is saying it has some OO features.

“I don't think it's incorrect to say has any more OOP than general purpose languages like Lua or JavaScript in that sense” = I think this language has more OOP than languages like Lua or JavaScript”

So, that more or less says “A, but A”. If so, what’s the “but” about?

I think it needs more negatives. "I don't think it's incorrect to say [it does not have] any more OOP than general purpose languages like Lua or JavaScript in that sense".

I had retyped it a few times trying not to come off as overly negative or a jerk.

> Not nothing, but I don't think it's incorrect to say has any more OOP than general purpose languages like Lua or JavaScript in that sense.

The comment is saying that the language has more OOP than Lua or JavaScript, but it seems like it might have been meant to say the opposite. That, and it appears to be missing a subject (which I assume to be ‘it’ or ‘the language in question’, based on context). So personally I do find it somewhat confusing.

The problem is not the double negative itself, though; it’s more how it’s being used in context here.

It was also to me. I also prefer simple clear language, so much for my feedback. Can we now move on?

Re "c)": No, self-hosting is the biggest temptation, and the worst mistake, for any programming language. It's death to bootstrapping. However, if you do succumb to the temptation to self-host, having a C backend, as Copper does, is probably the best way to handle it.

What's the problem with self-hosting? I do imagine it's easier to write a compiler in something like Haskell.

The problems with bootstrapping a self hosted compiler are often greatly overstated.

Self-hosting is a trivial matter if you can roughly map a subset of features of an existing language to your language. Write bootstrap compiler in that language and translator in parallel (as long as you have good AST/LST), run conformance tests on both.

As long as one of the backends is something widely available, I don't see a problem. C is a decent option. LLVM IR is another.

I've never really understood the opposition to self-hosting.

As long as:

* Your language is the kind of language that suits compiler development.

and

* You support compiling to C or something so that bootstrapping doesn't involve an opaque binary or compiling 30 different git commits in a row.

What are the downsides exactly?

The usual argument is that it is a distraction when you’re designing a language, and it leads to programming languages that are all excellent for writing compilers and parsers, but not particularly good for other things.

Since the majority of programs are not compilers, it might make more sense to focus on interesting things that aren’t relevant to compilers.

Some ideas from the top of my head: async I/O, a great SIMD story, effect systems, robustness systems for long-running processes (I’m only aware of Erlang/Elixir), and many others.

Compilers do exercise some things, like error handling and memory management, but they’re not particularly difficult or interesting in general.

This isn't at all true, as proven especially by Zig.

I would go so far as to say Zig even tries too hard to solve it (although they reused existing technology they already wanted, so it was almost free). You can bootstrap a self-hosted compiler to new environments by porting the source, cross-compiling it, and scp'ing or otherwise downloading it over to the target. And that's if you don't want to just use QEMU to develop it. We already do this exact thing when developing for embedded devices or often any type of aarch64 programs.

As someone who has monkeyed around with the zig compiler, having the bootstrap done made monkeying around way, way more straightforward than when it wasn't around. I will admit I don't know the details and it's possible the QOL improvements that affected me only depended on other things that got solved along the way. But I have been building the stage0 and stage1 compilers to get my first artifact when I bump to the latest.

Why is it harder to bootstrap a self-hosted language than it is to bootstrap a language implemented in C, which itself must be bootstrapped?

Bootstrapping is a one-time cost, but implementing the toolchain in C is a cost everyone has to pay every single time they touch the toolchain source.

Lampshading that you're doing something wrong doesn't make doing the thing less wrong. Hijacking a language post, of all things, to tell people some other completely unrelated project is better is ridiculously uncouth.

OOP is one of the weirdest topics in computer science in that no one can agree on what it means. Even proponents of “OOP” have wildly different ideas about what it means. For some it’s “encapsulation”, for others it’s “inheritance”, for others it’s “message passing”. It seems the glue that binds OOP proponents together is little more than the sequence of letters: O-O-P.

I drank the Elegant Objects[1] koolaid, and recommend the two books (Elegant Objects vol 1 and 2) whole-heartedly to anyone interested in OOP. Pony lang lets you write 95% of the kind of OOP described in the books idiomatically, without any kind of crazy shenanigans.

I think most people today would say encapsulation and message passing are pretty core to the definition of OO and inheritance is largely seen as an anti-pattern.

One thing I really like about Elegant Objects is that it is very palatable to FP enjoyers. Objects must encapsulate state, but they must also be immutable. Good OOP is declarative like good FP. It looks a lot like lisp imo. You're encouraged to code against interfaces instead of using inheritance etc.

[1]: https://www.elegantobjects.org/

Looks nice and small. Too bad it doesn't quite actually build (on Linux). Also, no string interpolation (AFAIC) and no kebab-case.

Here's my current stab at a small compiled language: <https://codeberg.org/stevefolta/lx-2025>.

As a Crystal fan, really nice syntax. The documentation leaves open several questions:

What is the memory model here? What does it compile to? What makes it 'low level'? Is there a GC? Does it have ABI compatibility with C or a FFI?

I wish the author has written about the motives behind the language and why someone should choose Copper. We have in fact more programming languages than we actually can use.

It is a personal project, which the author uses for some other personal projects.

Clade - a programming editor with elastic tabstobs and Smalltalk like navigation

Maybe, there is more. Looks to me like an illustration of the "It is a quiet life" meme

"Copper is a programming language that I use as a replacement to C."

That's used... to make what?

Seems for the other public project they've https://tibleiz.net/clade/ and its predecessor https://tibleiz.net/code-browser/.

How does it free memory? I don't get it. I browsed the docs a bit but didn't find a single reference to deallocation. There's alloc for heap allocation but no free?

In the standard library, there are some allocators with free, so it looks like you’re expected to call those. It is strange that none of the examples seem to cover this, though.

I think the days of releasing new programming languages is gone, it's like releasing a new punch card format. Humans don't code anymore and so programming language is really a choice LLM's make for you.

What leads you to think that? All the engineers I know always choose the language depending on the project details, scope, their own or team preferences, etc.

They ask Claude or some other model, this is the correct thing to do though, given it has the whole internet of software engineering history trained into its model and can read thousands of articles docs in seconds.

> Humans don't code anymore

I find that difficult to believe. Is there some objective evidence?

The ones that do are at a massive disadvantage, like someone writing out machine code by hand vs using a compiler back in the day.

Someone who can write assembly will always be at an advantage over someone who can’t. Yes even in the agentic era.

This feels like a photographer telling a painter that they're at a massive disadvantage and that no human paints by hand anymore. Meanwhile painters still exist and are probably not particularly upset by how many pictures per second a DSLR can do.

> like someone writing out machine code by hand vs using a compiler back in the day

Programming using a compiler is still the same kind of thing, just in a different language.

I was a programmer back in the day. That statement is simply misinformed.

This is a silly take. I think you underestimate how talented some programmers can be. I think you also overestimate how far being good at coding will get you. Pre-LLM, the job was maybe 30% coding. So at worst someone who codes by hand is only disadvantaged by a manageable amount.

I guess I’m not human

I can supply anecdotal evidence - of all the people I stay in touch with only one person occasionally opens IDE to write code. This transcends from interactive client apps through novel database engines.

AI is undergoing cosmic inflation, we get further apart faster.

Quite the contrary: the barrier to rolling your own <anything> was never lower.

As others have proclaimed: what matters is taste. And (perhaps?) a deep understanding of the subject matter. Which may or may not be encoded in formal specifications. But may also include 'fuzzy' domain-specific knowledge that can't be scraped from the web.

> Humans don't code anymore

I do, and I'm far from alone. Whether 'product' gains traction, that's another matter. But you know what? It doesn't matter. If it works for [author], that's enough.

Why? Did mathematics end when pocket calculators became popular? As today, the world initially overreacted (as usual): calculator opponents did warn about dependence, loss of arithmetic skills, and erosion of mathematical understanding. Making an existing exercise easier does not establish that the underlying discipline is in jeopardy.

"The days of the very thing happening here are gone."

Uh, no.

This seems to have a lot of potential, but there are important details missing. Hopefully the feedback from this thread will result in those questions getting answered by the author soon.

Seems really interesting

It’s nice they tried with a more fleshed out exemplar. Polymorphism (“generics”) and interfaces (“OOP”) would have been even better to see, especially across any kind of visibility boundary enforced by the language (packages, and the like.)

Programming to an abstract interface — and in large codebases, enforced visibility controls — represent the middle ground everyone wants, in my experience, between “OOP” and “sir, this is C”.

Yes,

The example definitely shines. Doing something barely non-trivial is great since it gives a feeling for the language. I wish other language introduction pages would take note.

I really like this language introduction.

It does feel like you need some shared understanding with the author about what the interesting parts of a programming language are and what can be left implicit.

Perhaps the author and I have similar intuitions? I guess I also like that isn't pure LLM output style. It was refreshing to see some human work.

> Polymorphism (“generics”) and interfaces (“OOP”) would have been even better to see

Yep. Interface-based (true) delegation between objects would be my go-to if it existed.

Subtyping and generics raise the question of whether containers are covariant or contravariant.

Really hard to make opinion based on few small examples but I can say I like what I see, Ruby like syntax definitely doesn't hurt language.

Multiple return values are kind of weird, but maybe it is just me. Overall this is something I will give a try.

Surprisingly, the most irritating nitpick for me is the choice of the file extension — surely that should've been ".cu", not ".co"? If I were developing an e.g. Iron programming language (hypothetically — although perhaps so named a language already exists), I'd pick ".fe" in a heartbeat.

Then again, I'm the kind of person who've chosen $'.\U0001F9CC' (that is, $'.\xF0\x9F\xA7\x8C') for a file extension of my own toy language so...

I like the way you think.

You're appreciated

Unfortunately for Copper in particular, .cu is associated with CUDA (so perhaps that’s why).

My first thought

Not a programming language, but Jane Street has (had?) a code review tool called Iron, abbreviated "fe".

https://blog.janestreet.com/code-review-that-isnt-boring/

And they’re not alone — mercurial is hg and the silver searcher is ag.

What about binding to external C ABI? I can haz Vulkan?

Hmm... Copper, I guess it must be great for representing lists. :-)

I'd like to come up with some constructive comments, but I find everything so inconsistent and alien to me...

For example, variable declarations use the pattern <colon> <type>, as in

  var a: Int32

But literals follow the opposite syntax, as in

  a = Int32: 42

The return type of a function is introduced by : in func definitions, but by -> in imported func declarations:

  func foo(a:Int):Int
  import func bar(a:Int) -> (Int)

Other construct that I find far from my habits:

  var w, h, d = 640, 480, 2

instead of the more obvious (for me):

  var w=640, h=480, d=2

Arguments are passed by ref, not by val. Good luck with recursion!

Agreed.. and what is going on with the `!` syntax? The docs are not exactly clear on the purpose in all cases.

https://tibleiz.net/copper/documentation.html#basic-syntax

The parallel assignment just work mostly like it does in ruby so that doesn't look weird to me (except the need for 'var' in the first place).

Agreed on the rest, though I don't understand what the problem would be with recursion. Is it using reference passing also for primitives like integers?

It's a bit like temple os :/

Is it memory safe? Or is it yet another "better C"?

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