luau VS Fennel

As far as I can tell, they aren't.

http://lua-users.org/wiki/SandBoxes

There is a lot of information there, but it doesn't handle resource exhaustion, execution time limits or give any guarantees. It does indicate that it's possible, and has a decent example of the most restrictive setup, which is a good start. But I would for example compare it with Luau's SECURITY.md.

From https://github.com/luau-lang/luau/blob/master/SECURITY.md:

> Luau provides a safe sandbox that scripts can not escape from, short of vulnerabilities in custom C functions exposed by the host. This includes the virtual machine and builtin libraries. Notably this currently does not include the work-in-progress native code generation facilities.

> Any source code can not result in memory safety errors or crashes during its compilation or execution. Violations of memory safety are considered vulnerabilities.

> Note that Luau does not provide termination guarantees - some code may exhaust CPU or RAM resources on the system during compilation or execution.

So, even luau will have trouble with untrusted code, but it specifies exactly what happens and so on. I think that's fair enough.

Alternatively, Luau is a well-supported Lua variant with type checking and performance improvements, aimed more towards being a sandboxed embedded scripting environment.

https://luau-lang.org/

If you need Lua but also type-safety, how about Luau [1] then?

[1] https://luau-lang.org/

I had the pleasure of working with Lua 5.1 back in the late noughties. For me it's replaced Tcl whenever I want something I can configure above a C library. At the time I used it I found it quite nice but I'll also not forget the hours I wasted tracking down nil table corruptions which could have easily been caught by a type checker.

I had some hope that Luau https://luau-lang.org or Teal https://github.com/teal-language/tl would make things better but with the following example

    function foo(x: number): string

Looking at other replies here, I can see I wasn't the only one who didn't realize there is Lua and Luau. Luau is an extension of Lua: https://luau-lang.org/

> Luau is syntactically backwards-compatible with Lua 5.1 (code that is valid Lua 5.1 is also valid Luau); however, we have extended the language with a set of syntactical features that make the language more familiar and ergonomic.

Lua is usually the embedded language of choice. If you are focused on security, you could check out the Roblox fork, Luau (https://github.com/Roblox/luau) where the creators took extra care to lock down the language on what scripts could do.

Luau - Lua variant by Roblox

On a side note, I've heard that they recently switched from Lua to Roblox's own fork of Lua, Luau.

https://www.youtube.com/results?search_query=luau+roblox&sp=...

Luau

https://github.com/Roblox/luau

Roblox wrote a superset of Roblox Lua which is way faster

https://luau-lang.org/ - some documentation, and examples https://create.roblox.com/docs - documentation, tutorials, and examples https://www.youtube.com/user/AlvinBLOX - tutorials https://www.youtube.com/@TheDevKing/videos - tutorials https://www.lua.org/manual/5.1/ - not specific to Roblox, but Lua reference manual https://www.codecademy.com/learn/learn-lua - Lua on Codecademy

It's interesting: minimal software is out there, but folks don't tend to choose it. I spend a fair amount of time thinking about how to be conservative in my dependencies, and this encourages a lightweight stack that tends to perform pretty well. These days, I'm favoring tools like Lua, SQLite, Fennel[0], Althttpd[1], Fossil[2], and the Mako Server[3] and find that great, lightweight, stable, efficient software is to be had, for free, but you have to go a bit off the beaten path. This isn't stuff you hear about on Stack Overflow.

In terms of frontend, which the post focuses on (Google Docs and a 30MB doc), I guess I'm conflicted. While I tend to favor native apps + web pages, I'm also a daily Tiddlywiki user, and I really think web apps have their place (heck, one idea I'm working on is a lightweight local server that lets you run web apps like Tiddlywiki). But without a doubt, Tiddlywiki is more resource intensive than Emacs (my go-to for notetaking when I'm not on TW). My tab for a 6MB Tiddlywiki file uses 155MB of RAM, and my (heavily customized, dozens of open buffers) Emacs session uses 88MB. So I do think the author has a good point.

[0]: https://fennel-lang.org/

Eh it's not just luajit and luajit didn't create that problem either. It's a symptom of lua actually succeeding at its design goal of being easily embedded as an extension language. A significant number of incompatible runtimes are more popular than the most recent puc lua, including I believe the older official lua 5.2 released in 2011.

I've done a fair bit of professional lua development and I don't think I've ever written standalone up-to-date puc lua except maybe for some tooling & scripts. It's such a small language and used in such a way that the runtime, distribution method, and available APIs have much more impact on your use (and compatibility) than the version.

Virtually everyone shipping a lua environment is also shipping changes to it that make it a unique target, if only extensions to the standard library. This is why I think syntax layer-only approach like fennel's is the correct choice for improving on lua. It mirrors lua's runtime semantics exactly, and allows you to access the implementation peculiars on their own terms and so can just be run on time of any lua system.

https://fennel-lang.org

Just learned about https://fennel-lang.org/ , could have probably used that as well to avoid Lua.

> I’m positive that there is a Lispy language out there (actually in existence, or the aether) that is appropriate for embedded work, but the constraints of the target make it difficult to envision.

Perhaps Fennel* fits the bill?

* https://fennel-lang.org/

I've also seen neovim plugins written in fennel [0], so if you want something lispy, that's possible now.

[0]: a Lisp that compiles to Lua, https://github.com/bakpakin/Fennel

Something similar: Fennel (https://fennel-lang.org/) is a lisp that compiles into Lua, which nvim can use as plugins, so you can write nvim plugins in a lisp. Aniseed (https://github.com/Olical/aniseed) makes this really easy.

If you want a more FP language on the Lua runtime, you might be interested in Fennel. I wrote a post about adding Fennel compiler to a hslua interpreter a while back, which might be useful for you.