Lily Programming Language
lily-lang.org58 points by FascinatedBox 4 days ago
58 points by FascinatedBox 4 days ago
What I really want to see from a "*-programming-language" post on HN is _why_. Why Lily?
I am curious as well. some past readme has Why sections and I am not sure why they are removed/changed
this have "Why" section https://gitlab.com/FascinatedBox/lily/-/blob/d3ace2907747106...
this have "How Lily stands out from other languages:" section https://gitlab.com/FascinatedBox/lily/-/blob/785a88534cced53...
The README on gitlab at least has a sentence or two on that: https://gitlab.com/FascinatedBox/lily
> An interpreted language with a focus on expressiveness and type safety
Personally I think typed scripting languages could be the future. They should support AOT compilation where necessary.
F# and C# are typed scripting languages. F# is quite similar to python in script form (.fsx), and has OCamls expressiveness, exhaustive pattern matching, and type inference. That results in highly expressive, terse, and ergonomic domain code.
The .Net VM now supports AOT compilation.
The future is now-ish :)
Why do you think that's the future?
Isn't a waste to essentially reinterpret an entire program that may be run 5000 times a day?
AOT compilation, how is that different than make && run?
At some point, you have a compiled language, if it's quick to compile, you're doing the AOT yourself, the scripting is an illusion. Pun intended.
> Isn't a waste to essentially reinterpret an entire program that may be run 5000 times a day?
This is a dated prejudice that I shared.
To get started coding with AI I made a dozen language comparison project for a toy math problem. F# floored me with how fast it was, nearly edging out C and Rust on my leaderboard, twice as fast as OCaml, and faster than various compiled languages.
Compiling could in principle be fastest, if we had compilers that profiled hours of execution before optimizing code, and only then for "stable" problems. No one writes a compiler like this. In practice, Just In Time interpreters are getting all the love, and it shows. They adapt to the computation. My dated prejudice did not allow for this.
Isn't it a waste to run a test suite for a program that would run 1M times a day in production?
The key adjective here is successfully run. You want to detect any errors as early as possible. Ideally even at the early stages of writing the script, when a typechecker is already able to point at certain errors, and thus help avoid missteps in further design.
a statically typed aot compiled scripting language is... not
I script with Rust via cargo-script, it works great. Scripting is a task for when you want to achieve something in one file instead of a full blown application. It is not about the language, you can script in C or assembly if you so chose.
"Scripting" is a role: an embedded, human-friendly, compact language, also suitable for interactive work / REPL.
(Laugh all you want, but Haskell has a rather nice REPL, and can work as a scripting language.)
Luau gets pretty close to statically typed and AOT compiled now. It's still a scripting language.
Even C or Rust can be a scripting language. You just integrate the toolchain to your app, same as every other scripting language.
> why
Building a program language is like poetry. Everyone does it at some point, just most of us know never to share it.
That just moves the question to "why is this one being shared" then. I don't think "because the authors didn't know better than to avoid sharing it like 'most of us'" is a particularly good answer.
From the link:
> Key features of Lily:
> Built-in template mode
> Embed/extend in C
> Single-inheritance classes
> Exceptions
> Generics
> Algebraic data types (with Option and Result predefined).
That’s what. Not why.
The why: because Lua, Python, JavaScript, Janet, etc lack many or all these features. And each of these features is known to make life easier for a human programmer.
Looking through that list of features, Ruby (the dynamic language I know best) has all but 1 built-in (and the other can be added with Gems). I'm guessing Python probably has them all too (but I don't know Python that well). They're pretty common. So the why still isn't clear.
Is Ruby easy to embed in a C program?
RPG Maker used to embed Ruby before it was cool (and before they switched to JS for web support).
Yes -> https://mruby.org
It's also incredibly easy to extend the main Ruby implementation with C, C++, Odin, Zig, Rust, Fortran, etc... Literally a few lines.
The main Ruby implementation is also fairly easy to embed. It's just not easy to embed multiple MRI ruby instances in a single application, and it's also a lot bigger than mruby.
The reason it exists is to provide those features when programming computers.
> statically-typed
> Embed/extend in C
Is Lily intended to be (or could it be used as) a statically-typed alternative to Lua?
Personally I'm happy with dynamic typing for scripting - but I suspect many people would welcome a statically-typed option, and there don't seem to be many available.
I’m a sucker for little embeddable languages but I’m even more of a sucker for rpn. Wonderful little example shows how simple of a math scheme it is.
One thing I very much appreciate in new-lang posts is seeing a code example above-the-fold, front and center. Kudos to the authors.
It uses refcounting, and GC for cycles. Sounds good. Why don't more Lua-likes?
Why not just use Ok/Error which is an accepted idiom and shorter than Success/Failure?
I see this so often in new languages, making poor choices seemingly only to distinguish themselves from existing languages
I would like to understand the motivations for building another programming language when in fact, firstly, a lot of code is being written by Claude and the like, and secondly, the existing languages and low level options like C, Assembly have become more accessible now thanks to AI coding tools.
> for v in values: {
Both colon and {... why? And it seems very mixed in the example.
I have no knowledge of lily, but a good reason could be for example that you can do `: print(v)`, but need braces for a multi-line block. Or that braces are the difference between creating a new scope and not. It's not necessarily just syntax for the sake of it.
Has anyone yet designed a language with the explicit goal of being cheapest/easiest to use by an AI coding agent?
January 2026 might be the month of langs created to be used by AI. Usually the chief concern is saving on tokens, prompted by context window anxiety. (This completely disregards the fact that agents thrash the context window by doing wrong things, then attempting to fix them; or by reading unrelated stuff; or by calling unhelpful tools; etc)
https://news.ycombinator.com/item?id=46450217 Nerd: A language for LLMs, not humans (1 Jan 2026)
https://news.ycombinator.com/item?id=46571166 Show HN: GlyphLang – An AI-first programming language (11 Jan 2026)
https://news.ycombinator.com/item?id=46583581 Show HN: B-IR – An LLM-optimized programming language (12 Jan 2026)
https://news.ycombinator.com/item?id=46684958 Nanolang: A tiny experimental language designed to be targeted by coding LLMs (19 Jan 2026)
See also
https://news.ycombinator.com/item?id=46582728 Which programming languages are most token-efficient? - where someone said "Someone has made a programming language called Sui, which is said to be designed for LLMs." https://github.com/TakatoHonda/sui-lang
And many other threads I didn't find right now
> Nerd: A language for LLMs, not humans
Interesting take, because I think precisely the opposite. Coding agents let us produce a lot of code, code that we need to read and review. That means we need languages optimized for code generation by AI, and code review by humans.
I see tons one them regularly here. And it's probably useless because LLM need a ton of training data
Not a language, but we are having very good success using https://brannn.github.io/simplex/ for autonomous one-shot workflows. It seems to be a very high-fidelity input for LLMs.