7 ms·

The compiler for Teal, a typed dialect of Lua

77 points by harporoeder 6y ago

pull_my_finger 6y ago
> Every type in Teal accepts nil as a valid value, even if, like in Lua, attempting to use it with some operations would cause a runtime error, so be aware! There has been a fair bit of discussion about this design decision/limitation recently in other channels. Seems like that's one of the main safety checks you'd want/expect from a compiler. That said - Pallene[1] and Nelua[2] are two very promising projects in similar spaces (although both are offering more than Teal's scope) [1]: https://github.com/pallene-lang/pallene https://github.com/pallene-lang/pallene [2]: https://github.com/edubart/nelua-lang https://github.com/edubart/nelua-lang
- veltas 6y ago
  In my opinion, this is a valid alternative and not a straight deficit. Lua demands using a lot of maybe-nil values, and 90% of the usefulness of types still applies if you 'hide' this. And there is a productivity gain from not having to consider nils in your types, because handling often requires code, annotation, or thought. But there is a loss of productivity to fixing nil errors that aren't caught by other typing features. Places where the typing in Teal is still helpful: accessing the wrong thing, typos of variable names, wrong number or type of arguments to functions. That covers most of the statically-detectable errors.
- hugomg 6y ago
  Pallene and Teal are in a bit of a different space. Teal is focused on compile-time type checking. The intention is to encourage you to add type annotations to your entire Lua codebase. It's another take at the problem that Typed Lua was trying to solve. A Typed Lua 2.0, if you want to call it that way. Pallene, on the other hand, is more focused on performance. The tradeoff is that it doesn't cover the entirety of the Lua language, just the features that we can generate fast code for. The intention is that you can write the performance-critical parts in Pallene and glue everything together using Lua (or Teal). That said, I certainly wouldn't be surprised if we saw more cross pollination of ideas between these two languages in the future :)
  - hisham_hm 6y ago
    > The intention is to encourage you to add type annotations to your entire Lua codebase. We definitely like to encourage the use of types (we <3 types!), but, just to clarify, Teal does support hybrid Lua/Teal codebases well, by use of definition files a la TypeScript. The Teal compiler itself is currently a "main program" written in Lua and the "core compiler" written in Teal. :) > A Typed Lua 2.0, if you want to call it that way. please don't, people are already confused as is. :) (For those not well-versed in Lua history like Hugo and me :), "Typed Lua" was an earlier academic project, which had different design criteria such as being able to type check unannotated "idiomatic" Lua, which made it a much more interesting research project and a much more difficult industrial one — Teal is very pragmatic, with the intention of being immediately usable but no intention of being academically interesting, more in the TypeScript mindset. This talk goes through the history, for those interested: https://www.youtube.com/watch?v=VUThGgxOf28 https://www.youtube.com/watch?v=VUThGgxOf28 ) > That said, I certainly wouldn't be surprised if we saw more cross pollination of ideas between these two languages in the future :) For sure! There are some exciting possibilities there!
layer8 6y ago
I wanted to create a language named Teal, just to be able to name the compiler Teal'c (or really tealc). I was disappointed the name was already taken, and even more disappointed the compiler is just tl.
- scrollaway 6y ago
  You could file a pull request. Hey maybe the linker could be called goauld.
- bungle 6y ago
  I guess now your only option is to go with STeal.
- nerdponx 6y ago
  Is this a pop culture reference?
  - lf-non 6y ago
    Yes. Teal'c is a fictional character [1] from TV Series Stargate SG-1 [1] https://en.wikipedia.org/wiki/Teal%27c https://en.wikipedia.org/wiki/Teal%27c
  - shakna 6y ago
    Teal'c is one of the main characters from the StarGate franchise, beginning with the first episode of SG-1.
  - gfaure 6y ago
    Indeed.
andrewmcwatters 6y ago
Andrew here from Planimeter, the guys who make Grid, the largest pure-Lua 2D game engine. https://www.planimeter.org/grid-sdk/ https://www.planimeter.org/grid-sdk/ One of the biggest difficulties I have with managing a project as large as Grid is, is that you just barely start to become large enough for one person to have difficulties not only keeping all the finer details in your brain, but writing extensive documentation is exceptionally time expensive. And we do a really bad job of it. We're supposed to be launching Grid Engine 10 sometime between now and March, but I don't think we're going to make it, because we haven't finished writing documentation for the next new major version. So I looked into tooling to get around these problems, but you have to hint at types in Lua comments. I also looked into typed variations of Lua, but there's a few, and some of them are all-or-nothing solutions. Teal has been out for a while, but I'm always pleasantly reminded of what exists in the Lua space, and how people continue to create great solutions for what I accept to be a more niche language. I hope that these solutions continue to be shared around on HN, because even though Lua's ecosystem is small enough for many of us to recognize one another, there's a lot more tech out there than Lua and you forget what people are working on. For as mature as Lua is, there are still complimentary solutions that are lacking in maturity or solutions that still don't exist all together. It's a very exciting space for developers.
- hisham_hm 6y ago
  Hi there! Hisham from Teal here. Yeah, Teal was motivated by my experiences developing LuaRocks, the Lua package manager, which is also a significant pure-Lua application, as well as other experiences working with large Lua codebases. We've been making some good progress on the compiler and the overall tooling (VS Code and Vim plugins, soon general LSP), and I can say that the overall development experience in Teal already feels smoother than pure Lua thanks to the compiler assistance. My intention with Teal is to be able to support use-cases such as yours, Love2D, and so on. In my FOSDEM talk earlier this month ( https://www.youtube.com/watch?v=OqXbnaDR8QY https://www.youtube.com/watch?v=OqXbnaDR8QY ) I mentioned some of the challenges involved in supporting more existing Lua codebases, and how I think we'll need to add a bit of a metaprogramming layer in order to support more smoothly things like homegrown class systems (like the one I see in Grid, in the very first example in your homepage). So I would love to get feedback as we start to explore this space. I want Teal to remain a minimalistic and pragmatic project, so the goal is not to develop a super-general meta-programming system, but one that solves concrete problems Lua developers face when integrating Teal.
diego_moita 6y ago
> It compiles Teal into Lua using We need better and more rigorous terms in computing science. This use of the compiler word blurs the meaning of interpreted vs compiled languages. I was under the assumption that it would generate executable machine code, not Lua source code.
- adamredwoods 6y ago
  transpiles? https://stackoverflow.com/questions/44931479/compiling-vs-transpiling https://stackoverflow.com/questions/44931479/compiling-vs-tr...
- munificent 6y ago
  > We need better and more rigorous terms in computing science. You can have terms that are precise and unchanging, and terms that are useful in today's computing landscape, but you can't have both. Grace Hopper, who coined the term "compiler" used it for what we'd today call a "linker-loader". Many C/C++ compilers emit textual assembly code which is then assembled as a separate step to machine code. The machine doesn't execute assembly, so are those still "compilers"? Nikaus Wirth's Pascal compiler compiled to bytecode, not machine code. Likewise, almost all Java and C# compilers today target bytecode and not machine code. Are they compilers? What if I take that bytecode and run it on a Java processor (https://en.wikipedia.org/wiki/Java_processor https://en.wikipedia.org/wiki/Java_processor)? Was javac not a compiler before Java processors existed but spontaneously became a compiler once the chip was shipped? The V8 JavaScript engine parses your JS, compiles it to bytecode, runs that in an interpreter, uses the results of that to re-compile the code to machine code, and runs that again. The user never explicitly invokes a compiler or sees any machine code written to disk. Is V8 an interpreter? A compiler? Both? If you never run a JS program long enough for the JIT to kick in, is it still a compiler? Some emulators for game consoles take game ROMs compiled to machine code for a different architecture and interpret them a virtual instruction at a time. Others take the ROM and recompile its machine code to new machine code for the host architecture, so they just treat the original machine code as an input format. Does that mean whether the ROM contains "executable machine code" versus "source code" depends on which emulator you run it in? When Apple transitioned from 68k to PowerPC, newer PowerPC Macs ran old 68k apps in an emulator. Did those apps still contain "executable machine code"? Modern CPUs implement large instruction sets by translating them down to microcode. If you compile to the larger ISA which is not what the chip actually executes, are you still outputing "executable machine code"?
redrobein 6y ago
Worth mentioning TypescriptToLua here I think. https://typescripttolua.github.io/ https://typescripttolua.github.io/

77 points by harporoeder 6y ago

> Every type in Teal accepts nil as a valid value, even if, like in Lua, attempting to use it with some operations would cause a runtime error, so be aware! There has been a fair bit of discussion about this design decision/limitation recently in other channels. Seems like that's one of the main safety checks you'd want/expect from a compiler. That said - Pallene[1] and Nelua[2] are two very promising projects in similar spaces (although both are offering more than Teal's scope) [1]: https://github.com/pallene-lang/pallene https://github.com/pallene-lang/pallene [2]: https://github.com/edubart/nelua-lang https://github.com/edubart/nelua-lang

veltas 6y ago
In my opinion, this is a valid alternative and not a straight deficit. Lua demands using a lot of maybe-nil values, and 90% of the usefulness of types still applies if you 'hide' this. And there is a productivity gain from not having to consider nils in your types, because handling often requires code, annotation, or thought. But there is a loss of productivity to fixing nil errors that aren't caught by other typing features. Places where the typing in Teal is still helpful: accessing the wrong thing, typos of variable names, wrong number or type of arguments to functions. That covers most of the statically-detectable errors.
hugomg 6y ago
Pallene and Teal are in a bit of a different space. Teal is focused on compile-time type checking. The intention is to encourage you to add type annotations to your entire Lua codebase. It's another take at the problem that Typed Lua was trying to solve. A Typed Lua 2.0, if you want to call it that way. Pallene, on the other hand, is more focused on performance. The tradeoff is that it doesn't cover the entirety of the Lua language, just the features that we can generate fast code for. The intention is that you can write the performance-critical parts in Pallene and glue everything together using Lua (or Teal). That said, I certainly wouldn't be surprised if we saw more cross pollination of ideas between these two languages in the future :)
- hisham_hm 6y ago
  > The intention is to encourage you to add type annotations to your entire Lua codebase. We definitely like to encourage the use of types (we <3 types!), but, just to clarify, Teal does support hybrid Lua/Teal codebases well, by use of definition files a la TypeScript. The Teal compiler itself is currently a "main program" written in Lua and the "core compiler" written in Teal. :) > A Typed Lua 2.0, if you want to call it that way. please don't, people are already confused as is. :) (For those not well-versed in Lua history like Hugo and me :), "Typed Lua" was an earlier academic project, which had different design criteria such as being able to type check unannotated "idiomatic" Lua, which made it a much more interesting research project and a much more difficult industrial one — Teal is very pragmatic, with the intention of being immediately usable but no intention of being academically interesting, more in the TypeScript mindset. This talk goes through the history, for those interested: https://www.youtube.com/watch?v=VUThGgxOf28 https://www.youtube.com/watch?v=VUThGgxOf28 ) > That said, I certainly wouldn't be surprised if we saw more cross pollination of ideas between these two languages in the future :) For sure! There are some exciting possibilities there!

layer8 6y ago

I wanted to create a language named Teal, just to be able to name the compiler Teal'c (or really tealc). I was disappointed the name was already taken, and even more disappointed the compiler is just tl.

scrollaway 6y ago
You could file a pull request. Hey maybe the linker could be called goauld.
bungle 6y ago
I guess now your only option is to go with STeal.
nerdponx 6y ago
Is this a pop culture reference?
- lf-non 6y ago
  Yes. Teal'c is a fictional character [1] from TV Series Stargate SG-1 [1] https://en.wikipedia.org/wiki/Teal%27c https://en.wikipedia.org/wiki/Teal%27c
- shakna 6y ago
  Teal'c is one of the main characters from the StarGate franchise, beginning with the first episode of SG-1.
- gfaure 6y ago
  Indeed.

andrewmcwatters 6y ago

Andrew here from Planimeter, the guys who make Grid, the largest pure-Lua 2D game engine. https://www.planimeter.org/grid-sdk/ https://www.planimeter.org/grid-sdk/ One of the biggest difficulties I have with managing a project as large as Grid is, is that you just barely start to become large enough for one person to have difficulties not only keeping all the finer details in your brain, but writing extensive documentation is exceptionally time expensive. And we do a really bad job of it. We're supposed to be launching Grid Engine 10 sometime between now and March, but I don't think we're going to make it, because we haven't finished writing documentation for the next new major version. So I looked into tooling to get around these problems, but you have to hint at types in Lua comments. I also looked into typed variations of Lua, but there's a few, and some of them are all-or-nothing solutions. Teal has been out for a while, but I'm always pleasantly reminded of what exists in the Lua space, and how people continue to create great solutions for what I accept to be a more niche language. I hope that these solutions continue to be shared around on HN, because even though Lua's ecosystem is small enough for many of us to recognize one another, there's a lot more tech out there than Lua and you forget what people are working on. For as mature as Lua is, there are still complimentary solutions that are lacking in maturity or solutions that still don't exist all together. It's a very exciting space for developers.

hisham_hm 6y ago
Hi there! Hisham from Teal here. Yeah, Teal was motivated by my experiences developing LuaRocks, the Lua package manager, which is also a significant pure-Lua application, as well as other experiences working with large Lua codebases. We've been making some good progress on the compiler and the overall tooling (VS Code and Vim plugins, soon general LSP), and I can say that the overall development experience in Teal already feels smoother than pure Lua thanks to the compiler assistance. My intention with Teal is to be able to support use-cases such as yours, Love2D, and so on. In my FOSDEM talk earlier this month ( https://www.youtube.com/watch?v=OqXbnaDR8QY https://www.youtube.com/watch?v=OqXbnaDR8QY ) I mentioned some of the challenges involved in supporting more existing Lua codebases, and how I think we'll need to add a bit of a metaprogramming layer in order to support more smoothly things like homegrown class systems (like the one I see in Grid, in the very first example in your homepage). So I would love to get feedback as we start to explore this space. I want Teal to remain a minimalistic and pragmatic project, so the goal is not to develop a super-general meta-programming system, but one that solves concrete problems Lua developers face when integrating Teal.

diego_moita 6y ago

> It compiles Teal into Lua using We need better and more rigorous terms in computing science. This use of the compiler word blurs the meaning of interpreted vs compiled languages. I was under the assumption that it would generate executable machine code, not Lua source code.

adamredwoods 6y ago
transpiles? https://stackoverflow.com/questions/44931479/compiling-vs-transpiling https://stackoverflow.com/questions/44931479/compiling-vs-tr...
munificent 6y ago
> We need better and more rigorous terms in computing science. You can have terms that are precise and unchanging, and terms that are useful in today's computing landscape, but you can't have both. Grace Hopper, who coined the term "compiler" used it for what we'd today call a "linker-loader". Many C/C++ compilers emit textual assembly code which is then assembled as a separate step to machine code. The machine doesn't execute assembly, so are those still "compilers"? Nikaus Wirth's Pascal compiler compiled to bytecode, not machine code. Likewise, almost all Java and C# compilers today target bytecode and not machine code. Are they compilers? What if I take that bytecode and run it on a Java processor (https://en.wikipedia.org/wiki/Java_processor https://en.wikipedia.org/wiki/Java_processor)? Was javac not a compiler before Java processors existed but spontaneously became a compiler once the chip was shipped? The V8 JavaScript engine parses your JS, compiles it to bytecode, runs that in an interpreter, uses the results of that to re-compile the code to machine code, and runs that again. The user never explicitly invokes a compiler or sees any machine code written to disk. Is V8 an interpreter? A compiler? Both? If you never run a JS program long enough for the JIT to kick in, is it still a compiler? Some emulators for game consoles take game ROMs compiled to machine code for a different architecture and interpret them a virtual instruction at a time. Others take the ROM and recompile its machine code to new machine code for the host architecture, so they just treat the original machine code as an input format. Does that mean whether the ROM contains "executable machine code" versus "source code" depends on which emulator you run it in? When Apple transitioned from 68k to PowerPC, newer PowerPC Macs ran old 68k apps in an emulator. Did those apps still contain "executable machine code"? Modern CPUs implement large instruction sets by translating them down to microcode. If you compile to the larger ISA which is not what the chip actually executes, are you still outputing "executable machine code"?

redrobein 6y ago

Worth mentioning TypescriptToLua here I think. https://typescripttolua.github.io/ https://typescripttolua.github.io/