Get the top HN stories in your inbox every day.
linkdd
aeternum
Since this is a Lua thread, your reference list should probably start at 1 rather than 0
afiori
It is about embedding how easy it is to embed lua, so you should be able to use the host conventions
anothernewdude
Oh wow, that does make the non-standard array references rather catastrophic.
BulgarianIdiot
Because of this I always thought lists should be iterable/traversable, but have no direct (numeric) index to their items.
stirfish
Like a stream?
cies
If you need a few line here an there scripting, sure Lua, JS, PHP... whatever works.
Using these languages for large projects is where the trouble starts: as they push you towards bad solutions that we know are bad for many decades. You need clear description of how to avoid these pittfals, or your growing codebase slowly becomes unmanageable.
I ended up ditching a growing Lua codebase for this reason. Get out before it gets to big to get out.
dbrueck
This opinion gets tossed around a lot, but I've found the opposite to be true, in part because all projects trend towards becoming an unholy mess as they grow large, so being able to accomplish a goal in significantly fewer lines of code has tangible benefits.
If there actually is a correlation between high level languages and "trouble", it may be just because a high level language lets a less experienced developer (or team of developers) get farther than they otherwise would in some lower level language, i.e. the more cumbersome nature of a lower level language forces you to follow best practices earlier or the whole thing never gets off the ground, while the same sloppy devs + a higher level language might actually get as far as shipping something.
Whether that is ultimately better is debatable, but the problem is more how the tool is being used than something inherent in the tool itself.
throw10920
> all projects trend towards becoming an unholy mess as they grow large, so being able to accomplish a goal in significantly fewer lines of code has tangible benefits
This is a really good point that I didn't realize before - sure, languages like bash and Lua and Tcl might scale very poorly to large codebases, but because they're more expressive than some other languages (coughjavacough), you might be able to implement the functionality you need without needing a large codebase in the first place.
pull_my_finger
I hear this opinion a lot. What exactly is the characteristic(s) that is missing from a scripting language? IDE integration? The compile-time checking before running? Seems like these problems largely have solutions these days. With stuff like JSdoc annotations or TypeScript, or Teal in Lua land, language servers for most languages etc, unit testing. They might be solved _better_ in a lot of compiled languages, but it's not like it's the Wild West if you're using a scripting language, and you could argue the more modern design in some of them are a fair trade-off for the native compile checking.
_0w8t
With Typescript you need to add an extra compilation step. With that one can just as well not to embed JavaScript but write in the original language.
Teal has an advantage that the typed language can be translated into Lua at runtime so during development it allows for quick prototyping and adding types when the amount of types becomes substantial. But its type system is less powerful than that of TypeScript.
cies
I do not prefer "scripting", but dynamic typing + poor language design.
There are dyn typed langs with langs with nice designs. I like Ruby and IOScript. All lisp-like languages. And there are several dyn typed fit-for-embedded langs implemented in Rust that are very promising. This is very much my own opinion, I know. But reading the article's "cons of Lua" I immediately remembered my fight with that language.
Personally I prefer typed languages nowadays. The stronger the better, as long as there is good IDE support.
undefined
zerocount
I'm not convinced scripting languages are not suitable for large projects. It's said a lot, but I've never seen proof one way or the other. I suspect unmanageable code-bases derive from uncontrollable project forces, ignorance, or not caring, but not because of the perceived short comings of a scripting language.
strenholme
Indeed. Unmanageable code bases come from conversations like this between management and developers:
“Look, we need you to implement this feature within the next 24 hours.”
“Based on my scrum analysis, I need about a week to implement it.”
“Sorry, if it’s not done within the next 24 hours, you will be out of a job.”
“OK....”
At which point, we get a hideous rush job. I have seen this happen time and time again. There is no language in the world which isn’t going to be able to force clean, manageable code under these kinds of circumstances, which alas can and do happen too often in the caffeine and work obsessed tech culture.
DoctorDabadedoo
It's a trade off, I think. A compiled static language forces you to behave a certain way at the expense of flexibility/expressiveness, script languages are more flexible, but in a way that is easier to acquire technical debt that might be harder to move away from (IMO).
xvilka
There's also Lua implementation (incomplete) in Rust - Luster[1].
strenholme
Some other implementations of Lua:
https://github.com/yuin/gopher-lua Lua in Go
https://github.com/fengari-lua/fengari Lua in Javascript
lmm
Why Lua rather than e.g. TCL or Python (both similarly easy to embed, but better-known as full-fledged languages)?
berkut
TCL's good for string stuff, but gets very messy if you want to do stuff outside of that. It wasn't really designed originally as a general language: it works and does have some (IMO 'too') clever features, but it has a lot of foot guns as well: comments are actually (almost) ignored procedures, which causes issues, you sometimes have to escape comments or they'll change logic or cause syntax issues (i.e. trying to comment out statements sometimes still triggers syntax errors within the comment!), everything's a string which is great for strings, but not when you need to start validating numbers or similar... TCL makes a lot more sense as a command language (what it was originally designed for - string commands) or a REPL...
Back in the late 80s before Python and Lua were released the following decades, TCL made sense, as it was the only freely available embedable language.
Python's larger and more complete (and I'd argue a better language then Lua), but Lua's compact and very fast as it's a register-based bytecode VM (and luaJIT exists which is even faster) (although if you don't use the 'local' keyword on variables, it's then quite a bit slower as it no longer uses stack-based variables, so the code can end up being more verbose to make it fast), so games commonly used Lua for scripting/gameplay as it was easy to integrate.
monetus
Have you seen TCL quadcode? It infers types and uses llvm - Check out the typing diagram; it is kind of crazy. Maybe it is to avoid shimmering more than anything, but I think it is impressive. Thought you might find it interestung even if you don't use TCL.
strenholme
Let me add my voice to the chorus of posters pointing out that, no, Python is not easy to embed.
Back in 2004 or 2005, Firaxis decided to use Python as their embedded scripting language. They used something called “Boost Python”, a then reasonably easy to embed fork of Python, to embed Python2 in their Civilization 4 gaming engine.
Soon after this, Boost Python got abandoned and Firaxis ended up having to use an outdated version of Python by the time they released their final Civilization 4 expansion.
For Civilization 5, Firaxis instead used Lua, since they wanted an actively maintained code base.
For my own “embed a scripting language in a DNS server” project, I went with a slightly modified Lua 5.1. The entire DNS server, including the Lua scripting engine, is a 103,936 byte sized Windows service. The stack was a little hard to grok at first, but I was able to fairly quickly get used to it and have a Lua script set up configuration for the server, as well as parse DNS queries. [1]
To Python’s credit, the Python2 code used in Civilization 4 is 100% compatible with the final 2019 release of a Python2 interpreter, to the point that I can run map scripts for Civilization 4 -- compiled for x86/32-bit -- on a 64-bit ARM Raspberry Pi and have them generate the exact same maps. Useful when I wanted a particular kind of map for a Civ4 mod, and had to iterate through 300 different random seeds on my Raspberry Pi to find the desired kind of map. After about a month, I had over 180 map seeds meeting my criteria.
[1] https://github.com/samboy/MaraDNS/tree/master/deadwood-githu... for the record
brandmeyer
Some corrections: Boost.Python (note the period) was a C++ library for automaticing the generation of cross-language bindings between Python and C++. It wasn't itself a distribution of Python. Boost.Python still exists. However, its successor (pybind11) used features shipped in C++11 to simplify the implementation (and compiles far faster) and is the leading Python-to-C++ binding to use today. I'm using pybind11 in a project today with bog standard Python3 and it works great.
Lua made inroads into the game dev community in particular thanks to LuaJIT. Despite it actually being a fork of Lua that hasn't kept up with changes in the base language, LuaJIT remains popular for its speed.
roblabla
Python is all but "easy to embed" - for one thing it's huge, and it requires linking to native libraries which may conflict with your own (openssl comes to mind). It also has an unstable ABI (and even API in some cases). Lua, in contrast, is just a single, very lightweight DLL, with no external dependencies and a stable ABI.
raverbashing
Yeah, Python is "theoretically" easy to embed, that's why it uses the GIL
In practice, it is hard to embed and we get the GIL disadvantages, so that is not working out so fine.
actuallyalys
My impression is that Python is not actually easy to embed (and I say this as a fan and frequent user of Python).
undefined
orthoxerox
Modern tcl is big. Embedding something like Jim is still possible, but I think Lua is more popular than tcl and has a more approachable syntax if you want laymen to use your DSL.
rauhl
Modern Tcl may be big, but it is not too big to embed. I know, because I embedded it into a Go system at a previous employer. Unfortunately, it is proprietary, so I may not point you to the repo, but it required remarkably little glue code.
I also evaluated Python and Lua. As others have noted, Python appears to be a right royal pain to embed. I actually had more experience with Lua prior to that project, but that experience leads me to believe that Lua is, generally, the wrong language.
Looking back on the project, I would not hesitate to do the same thing again, ideally as open source so that other Go projects can embed a scripting language. It got the job done, and did it well. Non-programmers on our team were able to write both configuration and logic successfully & productively, and apparently enjoyed the experience. Tcl itself ended up being a pleasure to use. While I personally would have enjoyed something like Embeddable Common Lisp, I think that would have been to much to ask of the rest of the team.
Interestingly, the four languages Lua, Python, Tcl and Lisp each can be said to take one idea and run with it. Lua is everything-is-a-hash-table (well, almost everything); Python is everything-is-an-object; Tcl is everything-is-a-string; and Lisp is everything-is-a-list (well, in theory: in practice it is really everything-is-an-object). I don’t know if this says anything deep about scripting languages, but it is at least interesting — right?
kayamon
Python is not easy to embed. It's very unsecure and is difficult, if not nigh-on impossible, to effectively sandbox. (see RestrictedPython)
progre
It's my understanding that Lua can be more easely sandboxed, at least compared to Python.
astrobe_
Lua is smaller, and one of the fastest in the bytecode-land. It also used in a large number of diverse applications [1], so in terms of popularity, I think it has nothing to be ashamed of compared to others.
[1] https://en.wikipedia.org/wiki/List_of_applications_using_Lua
leephillips
At first Lua seems strange, but after a while you start to appreciate it. It’s designed with a small number of concepts that manage to lead to expressive code with excellent performance.
I use it for two things: scripting TeX¹, where it allows you to do amazing things², even complex numerical calculations³ within the document; and writing Pandoc filters, where it is now the standard method.
1 ‘LuaTeX comes of age’. LWN. Available from: https://lwn.net/Articles/731581/
2 http://wiki.luatex.org/index.php/TeX_without_TeX
3 http://www.unirioja.es/cu/jvarona/downloads/numerical-method...
ludamad
I was a huge Lua fan, but once I jumped on the typescript bandwagon I found the lack of (production ready) desugaring and static type compilers for Lua to be a negative. The language is fantastic, but what I expect from a scripting language is always expanding, I guess
iamevn
You might enjoy https://typescripttolua.github.io/
I tried a bunch of different typed luas before landing on this project and having a really wonderful experience incrementally porting my most recent love2d thing over and then being able to make big architectural changes with confidence that types gave me.
I was able to do this port without modifying the original lua files, just replacing them with typescript one by one. Any lua libraries I was using I kept using by just writing some type declarations for then and throwing them in with the compiled output.
ufo
Today I would recommend checking out Teal: https://github.com/teal-language/tl/ I'd consider it the spiritual successor to Typed Lua.
ludamad
I looked at many options, what I lacked when I looked in this space is a big comparable project to, say, my game engine https://github.com/lanarts/lanarts that uses one of these typed Lua's. I'm not in a position where I can spend the time being the first - typescript has very mature idioms for large code bases
MapleWalnut
What about https://github.com/Roblox/luau? It gives Typescript-like annotations.
ludamad
With roblox behind it, I'd indeed consider it for my game. I'm guessing no support for LuaJIT, though?
nerdponx
I really appreciate that the article has a "Different" section for things that are different from, but not necessarily better or worse than, other programming languages.
This is also a very good summary, and tracks with my own experience getting into Lua for Neovim scripting.
spc476
This was written just after Lua 5.2 was released. There have been improvements since then. Lua 5.3 introduced an integer type (64-bit), actual Boolean operators, a UTF-8 library, a way to yield across a C-boundary and a way to pack and unpack binary data. Lua 5.4 introduced deterministic finalizers (and a fall out from that is a limited form of constant local variables).
rurban
But those improvements backfired, as Mike Pall refused to update luajit with them. They have now a 10x slower language implementation.
strenholme
If you want Lua which is luajit compatible, do what I did and use Lua 5.1 for the scripting engine. This way, if luajit performance is ever needed, scripts written with my engine will not break.
Lua 5.1 + bit32 (because, yes, I like to be able to do bitwise and/or/xor stuff) is my current favorite scripting language.
41b696ef1113
I wonder if maybe it was a good thing in the end. Lua51/LuaJIT are now dead languages - no new design changes are going to happen. It is now a stable development target for which libraries can only accumulate.
BoogerDan
Lua appeals to my sensibilites and I want to make use of it. It seems to be a well-designed language and it has a very performant JIT. But a big weakness for non-embedded use cases seems to be its ecosystem. A recent little project I wanted to use Lua on included a sqlite database, oldschool 3DES encryption, and an SMTP client. For many languages, there would be a clearly mob-approved library for each of these. But I found 3 or 4 possibilities to use sqlite in Lua, with no clear winner. I ended up using Ruby instead.
strenholme
While what you went through and felt is valid, I was able to find, in LuaRocks, libraries or Lua interfaces to libraries implementing everything on that wish list. In more detail:
a sqlite database
https://luarocks.org/modules/tami5/sqlite
https://luarocks.org/modules/dougcurrie/lsqlite3
3DES encryption
https://luarocks.org/modules/starius/luacrypto
https://github.com/somesocks/lua-lockbox/blob/master/lockbox...
an SMTP client
astrobe_
In my limited experience, when you want to interact with C libraries, you often end up reading the docs of the original C library anyway because often the bindings are nearly 1:1 - and often the trouble lies in the word "nearly".
Just writing yourself the bindings you actually need is most likely the best approach.
It should be relatively easy to do, because by using something like Lua you goal is precisely to expose functionalities implemented by your language as Lua functions (otherwise you would just convert them into dynamic library functions and use a classic glue language with a decent FFI to connect them).
This is the value proposition of an embeddable scripting language at heart.
monatron
I work on a project that leverages Kong's API Gateway, which is essentially Nginx + Openresty (Lua) + Kong (More Lua). The killer feature wrt Kong is the plugin ecosystem, which (among other things) allows you to act on the request/response lifecycle at various stages. Developers coming onboard to the project usually have little to no experience writing Lua, but we've found that coming up to speed on the language and it's runtime to be fairly painless. These days Kong has shims to write plug-in code in a few different languages (javascript, python, go, and more recently a wasm runtime) but despite our teams unfamiliarity with the language we still go back to Lua because performance can't be beat.
jonpalmisc
I’ve had a very positive experience using Lua as an extension language.
I was writing a text editor at the time. I wanted as much of the core code/actions to be written in Lua as possible, as I’ve always disliked very thin scripting APIs that sit on top of opaque native procedures.
I was able to wrap a handful of native functions in Lua code, then write the remaining 85% of the editor core in Lua. Everything was very fast and the process was straightforward. I’d definitely choose it again.
ufo
Lua 5.4 now includes a short utf8 library in the standard library. It has ways ways to get the utf8 string length and regex patterns for utf8 codepoints. However, it doesn't include any functionality that would require large tables of characters (for example, knowing which unicode characters are alphabetical).
-----
The requirement that return be the last statement is to avoid a syntactic ambiguity. Since Lua has no semicolons, there would be no way to know whether a line following the return statement is part of the return statement.
return
f()delusional
Would you not just terminate the return when you see a newline? like the language already does for expressions.
ufo
Newlines are not significant in Lua. From Lua's point of view, there is no difference between
return
f()
return f()
x=x+1 y=y+2abdusco
From a language design perspective, is it easier to build a compiler that considers `;` or newline as the end-of-statement operator, or one that works like Lua, where statements can appear anywhere?
delusional
I didn't know statements didn't need to be on separate lines. That's really cool. Thanks for the correction!
kdheepak
You can also write rust ( or go, or write in any other language that allows you to expose a C ABI ) and make a Lua module. This solves a number of the different, bad and ugly issues in my opinion. For example, I think using rust’s chrono or unicode_segmentation library makes life so much easier than having to deal with that in Lua. Neovim embeds lua 5.1 jit, and it’s possible to write plugins in rust for neovim using this mechanism.
For any one that knows what I’m talking about it should be obvious how to do this. If not, I wrote about this more here, in case you are interested:
https://blog.kdheepak.com/loading-a-rust-library-as-a-lua-mo...
1vuio0pswjnm7
Could have sworn I saw this submission 4 days ago.
https://news.ycombinator.com/user?id=Svetlitski
The timestamps next to the two oldest replies make it seem like they were more recently submitted, too. But I think they are 4 days old.
Seems like the title should be "Lua: Good, Different, Bad and Ugly Parts" as there is a fourth section, preceding "Bad", in the blog post called "Different".
Language wonks can endlessly dismiss Lua as a programming language, but it continues to be "embdedded in", i.e., used to extend, useful network applications, e.g., dnsdist, haproxy, nmap. To learn to use the application to its fullest, one has to learn some Lua.
josephcsible
That's the second chance pool: https://news.ycombinator.com/item?id=11657576
undefined
JonChesterfield
A missing 'good' - the reference implementation is extremely easy to extend with existing C or lua libraries. E.g. embed sqlite.c and bindings to it and all of penlight (a bunch of standard library like utilities written in lua).
There are some package managers. However concatenating all the source plus a bunch of libraries into one .c file also works great, My bootstrap/install is to clone that one file via git and feed it to clang.
dang
A couple past threads:
Lua: Good, bad, and ugly parts - https://news.ycombinator.com/item?id=6616817 - Oct 2013 (19 comments)
Lua: Good, bad, and ugly parts - https://news.ycombinator.com/item?id=5348513 - March 2013 (110 comments)
erwincoumans
It is nice small, so Lua even ran on Playstation 3 SPU!
We used to ship lua binaries for the premake build system.
For me, the indexed from 1 rather than 0 is a big turn off.
Roblox has the mlua fork, with increased performance and added type annotations: https://github.com/Roblox/luau
diego_moita
> For me, the indexed from 1 rather than 0 is a big turn off.
I can't understand why people complain about that.
If you're using 'pairs(table)' iteration then the index doesn't matter.
If you're accessing indexes directly you can have the index '0' in a table.
wheybags
> If you're accessing indexes directly you can have the index '0' in a table.
Sure, you can, but in practice you won't. For example, something like `local pos = {x, y}`. You now have to use 1/2 to access the x and y coords. Making the same table with 0 indexing is awkward and not idiomatic.
Get the top HN stories in your inbox every day.
Lua is a very nice piece of technology. Its source code is pretty easy to get into, the documentation is complete.
It has its quirks yes, but if I need to add scripting to a software, I'd consider Lua before considering writing a DSL, simply because you can pretty much embed Lua's source in your C/C++ software as a static library[0].
The stack-based approach makes it so easy to interact with C/C++, and I've been looking at the Rust bindings[1] recently out of curiosity, looks promising.