LuaJIT 3.0 proposed syntax extensions

pphreddypharkus about 2 hours ago 36 commentsRead Article on github.com

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Discussion (36 Comments)Read Original on HackerNews

Heliodex•about 2 hours ago

A comment <https://github.com/LuaJIT/LuaJIT/issues/1475#issuecomment-47...> has already been made on the issue regarding the ternary operator, recommending `if x then y else z` over `x ? y : z`. This is exactly how it's done with if-then-else expressions in Luau <https://luau.org/syntax/#if-then-else-expressions>, another language compatible with Lua, and makes it a ton easier to nest (especially with elseif) and I believe still easier to read than `y if x else z`.

mjcohen•about 1 hour ago

The ternary operator is easy to nest if you put each clause on a separate line. Then it looks just like nested if-then-else.

edoceo•42 minutes ago

I love the ternary operator as much as anyone. But dang if it doesn't get hard to read when there is are a few, nested even.

Does that operator compile to faster assembly that if I make the same logic with verbose `if` logic? Is that a language specific outcome?

gnubison•9 minutes ago

    cond1 ? res1 :
    cond2 ? res2 :
    cond3 ? res3 :
    or_else_res

If they are truly nested, then that is confusing. But if you have an if-else chain, then it can be quite readable.

omoikane•17 minutes ago

Lua 5.3 (2015-01-12) added the bitwise operators:

https://www.lua.org/versions.html#5.3

https://www.lua.org/manual/5.3/manual.html#3.4.2

Looks like LuaJIT is catching up, but calling these "syntax extensions" is confusing. Is the intent to hold LuaJIT fixed against some earlier Lua version (I guess 5.1) and adopt newer syntax piecemeal?

I welcome the compound assignment operators. Playdate's version of Lua also has that extension.

3eb7988a1663•about 2 hours ago

Never will I understand ternary operators. As soon as you introduce it, some chuckle heads want to use them everywhere. Worse if the syntax allows nested ternarys. I guess it keeps the language open for code golfing, but it otherwise seems like redundant syntax that at best saves a few characters.

201984•about 2 hours ago

Lua basically already has ternary operators anyway since "and" and "or" short circuit. I also don't see the need of adding additional syntax for it.

  local x = condition ? value_a : value b
  local x = condition and value_a or value_b

matheusmoreira•about 2 hours ago

> The classic Lua idiom a and b or c has a pitfall when b is nil or false: then c is returned, even when a is truthy.

> E.g. true and false or 42 returns 42, whereas true ? false : 42 returns the (expected) false.

demilicious•about 2 hours ago

That’s why “if” should just be an expression

matheusmoreira•about 2 hours ago

This is the best answer in my opinion. Ternary is just sugar for an expressive if. LuaJIT seems to be focusing on adding new syntax though, maintainer might not be amenable to updating existing semantics.

wavemode•30 minutes ago

I don't think if-expressions have to affect existing semantics. Basically, in the parser you would have two different kinds of AST nodes, one for when the `if` keyword is encountered in statement position and another for when it's encountered in expression position.

Right now, `if` in expression position is just a syntax error ("unexpected symbol")

hiccuphippo•about 2 hours ago

I find it most useful in languages that have non-mutable variables and you want to avoid a mutable variable or an extra function when the value comes from a simple condition.

Gualdrapo•about 2 hours ago

I guess for the JS case it makes sense to be able to shave a few characters for file shrinking purposes, but generally I'm more biased to code clarity and "self-explainability"

ianm218•30 minutes ago

Tangently related but I’ve been deep in Lua recently working on a rust implementation that supports Lua 5.1-5.5 in one Rust Binary https://github.com/ianm199/omnilua.

My ultimate goal was to support LuaJIT in Rust as well but this does not make it easier.

ricardobeat•about 2 hours ago

I see JavaScript.

Some of these really look like QoL improvements. I'm not convinced ternary statements are an ergonomic improvement in particular. The examples given don't make a compelling case, 'visually tidy' is not the same as readable.

nine_k•about 1 hour ago

Worse, I see C (as in ! or &&), and Perl (as in manifestly more than one way to do it).

There are real improvements though, such as ?. and ??= that help with default-nullable everything.

Ternary is very useful, but it I'd rather see it implemented idiomatically:

  pos += (if forward then +1 else -1)

Structural pattern-matching could be fantastic, but no syntax is suggested.

pansa2•about 2 hours ago

So is LuaJIT resuming active development after a decade or so of only maintenance? Great!

A lot of these changes make sense (although some of them are a bit too TIMTOWTDI for my taste) - but perhaps LuaJIT 3 would benefit from a change of name as well? Certainly with all these changes, it would be more like a separate language than merely a JIT-compiled version of Lua.

201984•about 2 hours ago

>TIMTOWTDI

What on earth is this supposed to mean?

Twirrim•about 2 hours ago

There Is More Than One Way To Do It.

That takes me back a bit. It's a perl-ism. I used to think it was a great design feature but I've come to strongly prefer "There should be one way to do it, and it should be obvious"

201984•about 2 hours ago

Interesting, thank you.

matheusmoreira•about 2 hours ago

There is more than one way to do it.

matheusmoreira•about 2 hours ago

Looks like LuaJIT is really going to fork away from Lua this time. After these changes, it won't be a compatible Lua 5.1 implementation anymore, it will be a new language.

So shouldn't it have a new name?

a_t48•about 1 hour ago

It could be opt in.

sourcegrift•about 1 hour ago

Are there any rough estimates on popularity of lua implementations? At this point it feels lua means luajit

latenightcoding•about 1 hour ago

not even close, because there are a lot of places where you can't run LuaJIT

bawolff•about 2 hours ago

+= and ..= are things i find i'm constantly missing in lua.

Personally im a fan of introducing ternaranary operator in lua. Everyone uses `x and y or z` as a ternanary which i find way more confusing than ?:

JSR_FDED•about 1 hour ago

What’s the Lua/LuaJIT story these days for bundling up all the scripts of an application into a single file? Is there a way to do the super convenient go-like thing?

linzhangrun•about 2 hours ago

I thought luajit had completely stopped feature updates

larrry•about 1 hour ago

I would love to see all of these come to LuaJIT (and love2d to support the new version too). It’s nice that Lua is simple, the syntax changes should hopefully make Lua code even simpler to read too

Rohansi•about 1 hour ago

> It’s nice that Lua is simple, the syntax changes should hopefully make Lua code even simpler to read too

But which Lua?

Lua as implemented by LuaJIT is a fork of the language at this point. It's not fully compatible with PUC Lua (the reference implementation) and LuaJIT does not support features from the latest Lua version.

le-mark•about 2 hours ago

I’m confused I thought Mike Pall left luajit and Laurence Tratt took over as maintainer?

dang•33 minutes ago

Mike Pall is to LuaJIT as PG is to Hacker News.

Edit: meaning he can come back anytime.

JSR_FDED•about 1 hour ago

Cool to see this - ergonomic syntax will make it easier to recommend Lua. Hope the PUC team aligns with this.

Also, I love this kind of pragmatism:

> Exponentiation assignment a ^= b has been deliberately omitted to avoid a predictable pitfall: this is how xor assignment is written in most other computer languages. Also, a syntax for exponentiation assignment is rarely asked for.

A ‘defer’ for closing files or deleting temp files at the end of a script will make life more enjoyable.

kibwen•about 1 hour ago

Please don't, inscrutable bitwise operators are an accident of the past even in systems languages, let alone in a scripting language. I'm not against infix operators for bitwise operations, just please spell them out with keywords rather than giving them sigils.

Likewise, going from `and` and `or` to `&&` and `||` would be a dispiriting regression. This is something that Zig got right.

JSR_FDED•about 1 hour ago

The btiwise operators library doesn’t go away

sourcegrift•about 1 hour ago

What are some pragmatic embedded scripting languages of choice these days if one has to consider:

1) Ease of learning, ideally minimal deviant behaviour (eg i consider lua tables to be a new concept in itself)

2) Reasonably fast. Not as much as lua jit but even half would be good enough

3) Mature

4) Has Rust bindings