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Lily Programming Language

lily-lang.org

75 pointsFascinatedBox48 comments

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What I really want to see from a "*-programming-language" post on HN is _why_. Why Lily?

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.

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 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.

> 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.

a statically typed aot compiled scripting language is... not

"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.

+1 for Luau which is just realy good.

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.

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 :)

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 reason it exists is to provide those features when programming computers.

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?

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.

That was originally the point of Ruby

RPG Maker used to embed Ruby before it was cool (and before they switched to JS for web support).

Tell me more about Ruby generics….

Want to split hairs eh?

Duck typing achieves the same thing as "generics", just at runtime vs. compile time.

Generics are implicitly compile time checks.

It’s a willful misinterpretation to read otherwise.

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...

> More importantly, this design makes it easy to compose whole programs that will never be paused by a garbage collection by avoiding cyclical structures.

Or by "breaking" cycles, which will trigger the reference count deallocation.

> 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.

99.9% of the time it will be "just because"

> 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.

Many of us would love a TypeScript analogy for Lua.

There have been some attempts:

Luau (5.2k, last week, https://luau.org/, https://github.com/edubart/nelua-lang)

Nelua (2.3k, 8 months ago, https://nelua.io/, https://github.com/luau-lang/luau)

Terra (2.9k, 3 days ago, https://terralang.org/, https://github.com/terralang/terra)

Teal (2.7k, 2 days ago, https://teal-language.org/, https://github.com/teal-language/tl)

The Luau author is always on the official Lua mailing list, and it has twice as many stars, so it seems likely to win the long term popularity contest.

Also it looks like[1] Luau is the official Roblox Studio scripting language, and is baed on Lua 5.1 (possibly LuaJIT?) which means it's behind mainstream Lua.

Not sure which Lua versions the others are based on.

[1] https://create.roblox.com/docs/luau

Note that some of those can't run on a regular Lua runtime.

Luau is a separate implementation of a Lua dialect. However, it's backed by Roblox and being increasingly used in high budget games such as Alan Wake 2, and tools like Rive.

And Terra is more of a low-level language embedded in regular Lua for metaprogramming, than a statically-typed Lua.

In this vein there's also Pallene, which integrates better with regular Lua on a slightly-patched Lua runtime.

https://github.com/pallene-lang/pallene

(BTW the links for Nelua and Luau repos got mixed.)

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.

And not only math. See Forth as a reference.

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.

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

> 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.

It uses refcounting, and GC for cycles. Sounds good. Why don't more Lua-likes?

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.

Well, it's like a few people still make music, even if there is Suno ;-)

Has anyone yet designed a language with the explicit goal of being cheapest/easiest to use by an AI coding agent?

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.

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)