One of the new features I found interesting, declarations for global variables, is buried in the reference manual. Here's a link to the section that discusses it: https://www.lua.org/manual/5.5/manual.html#2.2
ConTeXt has been using beta versions Lua 5.5 for a few years now, so you can look through its source [0] or try running it [1] if you're curious what a large codebase written in Lua 5.5 looks like.
I feel like Lua is absolutely underrated. I just wish one of the mainstream browsers actually puts their foot down and starts supporting Lua as scripting language.
This sounds like an offhand Youtube comment, I'm afraid. Underrated how? Its principal strength, easy embedding with the ability to work as an extension language, is well known in the circles where it matters. The authors never gave an impression that they'd aim to make it a language to bury all other scripting languages, which I find refreshing in the winner-take-all culture of programming language discussion. Lua is modest and works well for what it is. No need to go all grandiose.
> I just wish one of the mainstream browsers actually puts their foot down and starts supporting Lua as scripting language.
I sincerely hope not, that would be a very counterproductive dilution of effort. Browser authors already have their plate full with all other web platform problems.
One of the super powers of Lua is that it doesn't need to be very stable: because you are always embedding an interpreter your code and interpreter have a matching version.
That's directly contrary to what would make it acceptable as a web spec, compared to e.g. wasm being powerful enough to be a compile target that can support wasm.
Ypu could probably run it in wasm. Of course, without access to the DOM it won't go any further than anything else on wasm. The whole thing is nuts if you ask me. So much lost potential.
Not true. It's getting a constant stream of bugfixes. It's also not "stuck" on Lua 5.1, but is deliberately not following Lua's path, except for some backports. There's also a recent post about how a LuaJIT 3 might work.
Well. You’d have to demonstrate that a[1] is the first offset in an array, and it’s not a great curb appeal to anyone who has programmed computers before.
Seems like an odd change, I wonder what the rationale is. Just making it clear to people new to the language that you can't adjust it mid-loop to change the loop count I guess?
The control variable in for loops is read only. If you need to change it, declare a local variable with the same name in the loop body.
Also [0]:
Roberto Ierusalimschy
> So what's the rationale to make them constant now? Does it have performance
> reasons?
Yes. The old code does an implicit "local x = x" for all loops, in case
you modify 'x'. With the new semantics, the code only does it when you
ask for it.
In previous versions, you could change it mid-loop. This apparently caused some unintuitive behavior when paired with generators (e.g. `for k, v in pairs(table)`).
I haven't run into this myself, but it does make sense, and eliminating this footgun sounds like a good idea.
Only a dabbler in Love2d here but I’d expect that update to be a bit down the line. If I’m not mistaken the current Love2d version 11.5 is (mostly) tied to Lua 5.1 because of LuaJIT, though I understand some later Lua features are backported. And the changelog for the in-dev 12.0 release talks about compiling Love2d for Lua 5.4 as if it’s an optional thing.
I don’t really follow LuaJIT too closely so I’m not sure if they’re even targeting Lua 5.4 let alone 5.5. I remember reading some GitHub issue that suggested some of the design decisions in Lua 5.4 wouldn’t really support LuaJIT goals re: performance.
With that said I’ve been enjoying Love2d even with Lua 5.1 features — as a hobbyist it works just fine for me.
Would certainly appreciate any corrections by those more in-the-know though!
Cannot wait for another version of Lua to sit unused basically everywhere.
Truly is a shame, everything seems to have settled on 5.1 for the most part without ever being updated, or any intention of it being updated. Some really nice features post 5.1
I understand each version of Lua introduces breaking changes in the language, which isn't great as the language becomes fragmented (Or not really, once again 5.1 is pretty ubiquitous)
The real reason everyone settled on Lua 5.1 is because that's the version LuaJIT is compatible with, and most people are unwilling to give up the performance gains.
5.1 (by way of LuaJIT) gets a lot of use, but to suggests no one uses the modern versions is just not true. Lua being an embedded language just takes the pressure away to upgrade. It's a feature, not a bug.
1. The luajit documentation basically just had a list of features. AFAIK there isn't any documentation that combines the 5.1 reference with luajit extensions (including things that were backported)
2. In some cases, for example Neovim, luajit extensions aren't guaranteed to be available. It just says there will be a lua runtime compatible with 5.1. Which means a truly portable neovim plugin can't use those extensions
3. There are features from later lua versions I would like to have (in particular <const> and <close>) that will probably never get backported.
4. Some features require luajit to be built with special flags
I never coded in Lua but I found out recently that Lua is now in FreeBSD base [0]
This is huge for Lua and FreeBSD.
Now something that worry me is whenever you need to make an HTTP request or parse some JSON you need to go on a quest for a "library" on the Internet. It doesn't seems to have a (semi-)official "Extended Standard Library" I can quickly trust.
The Lua ecosystem is more like the Lisp ecosystem than Python. The language is small enough that there’s a lot of stuff out there that’s just… finished. Hasn’t been updated in 10 years but still works. The LunarModules org tries to gather it up and keep it compatible.
Lua is really designed as an extension language but it’s such a nifty little language that sometimes you really wish you could use it in place of Python or Perl, which is why LuaJIT is so popular. But LuaJIT is really just one guy’s project. Its metaprogramming features are really nice and let you build some Lisp-style DSLs, and if you want full Lisp syntax you can drop in Fennel. If you’re just writing extension code you often don’t need a standard lib because it’s easier just to roll your own function to fill the gap.
Personally, I found it easier and quicker to just read the reference manual to learn the language. It’s small and simple enough that you shouldn’t have trouble getting up to speed if you have a couple other imperative languages under your belt. IMO metatables are much easier to work with than JavaScript’s prototype inheritance.
Interesting, it looks like you can use ´global myvar’ now, as compared to ´myvar’ implicit globals, say from back in 5.1, or ´local myvar’.
It’s worth noting that global is a reserved keyword now, so environments that had a ´global()´ function for escaping environments will now need to rename their helper function.
But.. why ? Globals are just variables that reside in the wrapping env table that also contain the C functions. If a closures is a onion of table lookups out of the function context from local -> function scope -> global scope is simply the last lookup before a not found variable with nil is declared?
[0]: https://codeberg.org/contextgarden/context
[1]: https://wiki.contextgarden.net/Introduction/Installation
This sounds like an offhand Youtube comment, I'm afraid. Underrated how? Its principal strength, easy embedding with the ability to work as an extension language, is well known in the circles where it matters. The authors never gave an impression that they'd aim to make it a language to bury all other scripting languages, which I find refreshing in the winner-take-all culture of programming language discussion. Lua is modest and works well for what it is. No need to go all grandiose.
> I just wish one of the mainstream browsers actually puts their foot down and starts supporting Lua as scripting language.
I sincerely hope not, that would be a very counterproductive dilution of effort. Browser authors already have their plate full with all other web platform problems.
That's directly contrary to what would make it acceptable as a web spec, compared to e.g. wasm being powerful enough to be a compile target that can support wasm.
That's huge. I wish LuaJIT adopted this, or at least added a compile time flag to enable it.
Seems like an odd change, I wonder what the rationale is. Just making it clear to people new to the language that you can't adjust it mid-loop to change the loop count I guess?
Yes. The old code does an implicit "local x = x" for all loops, in case you modify 'x'. With the new semantics, the code only does it when you ask for it.
[0] https://groups.google.com/g/lua-l/c/SlAG5QfpTac
I haven't run into this myself, but it does make sense, and eliminating this footgun sounds like a good idea.
I don’t really follow LuaJIT too closely so I’m not sure if they’re even targeting Lua 5.4 let alone 5.5. I remember reading some GitHub issue that suggested some of the design decisions in Lua 5.4 wouldn’t really support LuaJIT goals re: performance.
With that said I’ve been enjoying Love2d even with Lua 5.1 features — as a hobbyist it works just fine for me.
Would certainly appreciate any corrections by those more in-the-know though!
Truly is a shame, everything seems to have settled on 5.1 for the most part without ever being updated, or any intention of it being updated. Some really nice features post 5.1
I understand each version of Lua introduces breaking changes in the language, which isn't great as the language becomes fragmented (Or not really, once again 5.1 is pretty ubiquitous)
Not exactly. LuaJIT has backported various hot features from 5.2 and 5.3 as long as they're unlikely to break 5.1 code.
1. The luajit documentation basically just had a list of features. AFAIK there isn't any documentation that combines the 5.1 reference with luajit extensions (including things that were backported)
2. In some cases, for example Neovim, luajit extensions aren't guaranteed to be available. It just says there will be a lua runtime compatible with 5.1. Which means a truly portable neovim plugin can't use those extensions
3. There are features from later lua versions I would like to have (in particular <const> and <close>) that will probably never get backported.
4. Some features require luajit to be built with special flags
I think the real LuaJIT is strictly 5.1
https://luajit.org/extensions.html
Now something that worry me is whenever you need to make an HTTP request or parse some JSON you need to go on a quest for a "library" on the Internet. It doesn't seems to have a (semi-)official "Extended Standard Library" I can quickly trust.
- [0] https://man.freebsd.org/cgi/man.cgi?query=flua&apropos=0&sek...
For an extended standard lib, the closest thing is probably Penlight. https://github.com/lunarmodules/Penlight If you want async IO, sockets, etc, check out Luvit. https://luvit.io
Lua is really designed as an extension language but it’s such a nifty little language that sometimes you really wish you could use it in place of Python or Perl, which is why LuaJIT is so popular. But LuaJIT is really just one guy’s project. Its metaprogramming features are really nice and let you build some Lisp-style DSLs, and if you want full Lisp syntax you can drop in Fennel. If you’re just writing extension code you often don’t need a standard lib because it’s easier just to roll your own function to fill the gap.
Personally, I found it easier and quicker to just read the reference manual to learn the language. It’s small and simple enough that you shouldn’t have trouble getting up to speed if you have a couple other imperative languages under your belt. IMO metatables are much easier to work with than JavaScript’s prototype inheritance.
It’s worth noting that global is a reserved keyword now, so environments that had a ´global()´ function for escaping environments will now need to rename their helper function.