5 ms·

Bootstrapping a Forth in 40 lines of Lua code

122 points by anothername12 2y ago

veqq 2y ago
As eval() was removed from Lua, you must reimplement it: ``` function eval(s) load(s)() end ```
- aeonik 2y ago
  For those who don't know Lua very well (like me), here is a link to the reference manual. https://www.lua.org/manual/5.4/manual.html#pdf-load https://www.lua.org/manual/5.4/manual.html#pdf-load A simple example that I tested: local chunk = "return 2 + 2" local func = load(chunk) print(func()) -- Output: 4
  - CapsAdmin 2y ago
    loadstring lwas replaced with load, and dostring was removed, but it's basically just assert(loadstring(code))(...) load is the replacement. i assume the grandparent meant dostring and not eval?
bmitc 2y ago
I need to do something with either of these languages. I've learned Forth before but never did anything with it. I should learn Lua as well.
- aeonik 2y ago
  The two Forths that I've had my eye on: https://www.gnu.org/software/gforth/ https://www.gnu.org/software/gforth/ And the inventor of Forth has a very power efficient multi-computer chip that can be programmed with colorForth or array forth (he claims most power efficient): https://www.greenarraychips.com/home/products/index.php https://www.greenarraychips.com/home/products/index.php https://www.greenarraychips.com/home/documents/greg/cf-intro.htm https://www.greenarraychips.com/home/documents/greg/cf-intro... Here is a video about the chip, and some cool Forth demos with it: https://youtu.be/0PclgBd6_Zs?si=nThy9TnGl9rJX5_u https://youtu.be/0PclgBd6_Zs?si=nThy9TnGl9rJX5_u
- turtledragonfly 2y ago
  I've had a very enjoyable experience with Lua, and kaguya for binding it to C++. Match made in heaven, for the most part (: PUC Lua also has a very solid coherent C implementation; it's basically a masterclass in making an effective, portable, but also necessarily complex C library.
  - binary132 2y ago
    Lua is definitely a pedagogic language and project all the way to its roots. I often feel like I’m taking a class on compilers when using it. :)
- IncreasePosts 2y ago
  Forth is super interesting, and worth learning, but it seems like an evolutionary dead end. Even Chuck Moore doesn't do much Forth these days, because he doesn't like having to keep track of a whole bunch of details that keep getting changed between processor families.
  - chuckadams 2y ago
    Chuck Moore designs processors, seems to me he's got those details handled. Last thing I heard he worked on was etherForth, but the guy's 85 years old, so he might just have quietly retired by now. Forth was never going to be the next Java or Rust, but in its own little niche, it's fantastic. ANS Forth isn't getting any new features anytime soon, but meanwhile forth spawned a whole family of interesting languages like Joy, Factor, and ColorForth. Besides, evolution is overrated: tardigrades are still doing fine :)
    - andsoitis 2y ago
      > evolution is overrated: tardigrades are still doing fine :) The evolution of tardigrades as super fascinating: https://eartharchives.org/articles/tardigrade-genome-reveals-secrets-of-their-toughness-and-evolution/index.html https://eartharchives.org/articles/tardigrade-genome-reveals...
  - 7thaccount 2y ago
    Chuck gave up doing Forth in assembly for modern processors a number of years ago, but developed the GreenArrays chips that are apparently like 144 computers on a chip. He programs that in some version of ColorForth and has done several talks on it. I have no clue if there is any value because I can't understand it's use case. It is really cool though that when he builds an application, he typically understands everything from the machine level all the way through the software and he designs them both to some kind of optimal overall system. He's got to be one of the only people alive who can still claim that I'd guess.
    - chuckadams 2y ago
- larsbrinkhoff 2y ago
  Tradition has it that the thing to do with Forth is implement your own toy and then call it a day. Usually not having learned how to actually program in Forth. Yes I'm bitter.
- JBits 2y ago
  If you're looking for something to do in Lua, I suggest making a game with the Love2D framework [love2d.org]!
  - bmitc 2y ago
    I've had my eye on it for sure!
thefaux 2y ago
Lua and Forth is like pb&j.
mjevans 2y ago
It'd be interesting to see how compact the binary form is, and what external dependencies it has. Forth's selling points are mostly how compact a minimal environment can be, and how easy it is to extend that environment to do more useful things. The 'shell' is the compiler.
rasur 2y ago
I 'learned' Forth decades ago (on a Sinclair ZX81, so essentially a quite horrible experience), and tripped over it again recently.. ending up ploughing through the books "Thinking Forth" and (currently) "Starting Forth" both of which are extremely interesting and so very very different to what we use these days. It very much fits into that saying "A language that doesn't change how your think about programming, isn't worth knowing". I realise now just how shallow an understanding of Forth I had as a teen, back in the day ;) But I think the win here - these days - for Forth is in things like "running on small embedded devices".. I'm looking with interest at some of the activity around say Arduinos and am thinking that Forth is a rather nice fit for that sort of system. Have bought a kit, and am looking forwards to some non-work quality time to play further :) (The Books I meantion can be found online very easily, but you'll forgive them for being written back in a time when systems were _simpler_ to grok ;) )
- _0ffh 2y ago
  > I think the win here - these days - for Forth is in things like "running on small embedded devices" In principle that's not a bad idea, it's just that you're at least 40 years late to the party. FORTH was and propably is used in embedded systems for most of it's existence. Often simply with a minimal text console over UART, that being your "way in". Once you've got that going you can start builing up your system from the inside.
  - rasur 2y ago
    Being late to the party is the story of my life, but fwiw, I was aware that FORTH was used a lot in this kind of use-case ;)
- rwmj 2y ago
  Artic Forth? I had a lot of fun with that. https://worldofspectrum.net/item/0031896/ https://worldofspectrum.net/item/0031896/
  - rasur 2y ago
    I think it was, actually, yes. Thanks for the reminder!
RetroTechie 2y ago
Trying to get an overview of which languages allow for tiny implementations of their core features. Like, max. ~10KB binary size (but preferably a few KB's). This is assuming basic IO is trivial, like reading/writing to some memory location to get/print a character on text console. Forth is an obvious one. Basic another. There's some tiny Lisps out there. And Tcl. Any other languages that go that small?
- giraffe_lady 2y ago
  One thing you quickly run into with this exercise is needing to establish the boundaries around "programming language" which can be kind of fraught. For example miniKanren is tiny and is used as a DSL, but is capable of expressing any computation so does that count? Some type systems are turing complete and a naive implementation could be tiny. Is conway's game of life a programming language. You could probably strip a bunch of useful stuff out of sqlite's sql parser and get it below 10k. etc.
  - samatman 2y ago
    You have to draw a line somewhere, and it's necessarily somewhat arbitrary. Mine is the size of the runtime, usually. So the Forth is the size of Lua + the 40 line script, minKanren is the size of the .scm file + the Scheme implementation, and so on. This ignores the host environment, which I think is fair: generally these will be enormously larger than they would actually have to be to support the language. I do award subjective bonus points to languages which actually have a freestanding runtime, that is, I could actually compile them and run them on a bare chip. Even then, I don't count the microcode which implements the instruction set of that chip, or the Verilog/VHDL which is needed to tape it out. Usually! ColorForth on GreenArrays gets even more bonus points, because not only is the language exceedingly compact, and freestanding, but the VLSI tool used to create the chip is also tiny to an almost unbelievable degree. So it wins some kind of prize in the special "total system complexity" category.
    - RetroTechie 2y ago
      > I do award subjective bonus points to languages which actually have a freestanding runtime, that is, I could actually compile them and run them on a bare chip. That's what I was getting at with "trivial IO": when you ignore what's needed to get data in/out, and optional parts of a standard library (if included), how big is the remainder, the implementation of the language constructs? (Potentially) standalone, self-hosting & small is indeed the bonus points I'm looking for. A tiny Basic or Forth running bare metal on a uC could be it. A 'tiny' language implemented using a multi-MB VM is not.
pjmlp 2y ago
While a great exercise and kudos to the author, I think languages like Forth and Lisp are much cooler to bootstrap from Assembly. Anyway, thanks for sharing.
- samatman 2y ago
  Assembly? Hah! It only counts if you use a magnetic needle and a very steady hand.
  - pjmlp 2y ago
    From that point, first we need to mold some gears.
zelphirkalt 2y ago
Is there any Forth, that properly handles unicode strings, by which I mean, that it has sensible string length, substring and such functions or some standard library that has them? Basically all the usual stuff one needs. I tried to use GForth a while ago, but how to use strings properly was a mystery. I don't want to have to code all string functionality myself. Well, neither do I know how, nor do I want to. I guess I would have to study other languages' implementations and some standard documents or so for that, when actually I am doing another project. A gigantic rabbithole that would be. Afaik there is more planned in the 1.0 release of GForth. Reading line after line from a file was also difficult. I could not figure out, how to clear the storage used for the previous line properly. When I read a shorter line after a longer line, the storage would still contain the longer part of the longer line after the content of the shorter line. Perhaps there is a Forth that makes this easy? But it also needs to support that library, FFL, so that I have useful data types, and don't need to roll my own arrays or something ... Maybe my design philosophy is fundamentally different from what is needed for Forth?

122 points by anothername12 2y ago

veqq 2y ago

As eval() was removed from Lua, you must reimplement it: ``` function eval(s) load(s)() end ```

aeonik 2y ago
For those who don't know Lua very well (like me), here is a link to the reference manual. https://www.lua.org/manual/5.4/manual.html#pdf-load https://www.lua.org/manual/5.4/manual.html#pdf-load A simple example that I tested: local chunk = "return 2 + 2" local func = load(chunk) print(func()) -- Output: 4
- CapsAdmin 2y ago
  loadstring lwas replaced with load, and dostring was removed, but it's basically just assert(loadstring(code))(...) load is the replacement. i assume the grandparent meant dostring and not eval?

bmitc 2y ago

I need to do something with either of these languages. I've learned Forth before but never did anything with it. I should learn Lua as well.

aeonik 2y ago
The two Forths that I've had my eye on: https://www.gnu.org/software/gforth/ https://www.gnu.org/software/gforth/ And the inventor of Forth has a very power efficient multi-computer chip that can be programmed with colorForth or array forth (he claims most power efficient): https://www.greenarraychips.com/home/products/index.php https://www.greenarraychips.com/home/products/index.php https://www.greenarraychips.com/home/documents/greg/cf-intro.htm https://www.greenarraychips.com/home/documents/greg/cf-intro... Here is a video about the chip, and some cool Forth demos with it: https://youtu.be/0PclgBd6_Zs?si=nThy9TnGl9rJX5_u https://youtu.be/0PclgBd6_Zs?si=nThy9TnGl9rJX5_u
turtledragonfly 2y ago
I've had a very enjoyable experience with Lua, and kaguya for binding it to C++. Match made in heaven, for the most part (: PUC Lua also has a very solid coherent C implementation; it's basically a masterclass in making an effective, portable, but also necessarily complex C library.
- binary132 2y ago
  Lua is definitely a pedagogic language and project all the way to its roots. I often feel like I’m taking a class on compilers when using it. :)
IncreasePosts 2y ago
Forth is super interesting, and worth learning, but it seems like an evolutionary dead end. Even Chuck Moore doesn't do much Forth these days, because he doesn't like having to keep track of a whole bunch of details that keep getting changed between processor families.
- chuckadams 2y ago
  Chuck Moore designs processors, seems to me he's got those details handled. Last thing I heard he worked on was etherForth, but the guy's 85 years old, so he might just have quietly retired by now. Forth was never going to be the next Java or Rust, but in its own little niche, it's fantastic. ANS Forth isn't getting any new features anytime soon, but meanwhile forth spawned a whole family of interesting languages like Joy, Factor, and ColorForth. Besides, evolution is overrated: tardigrades are still doing fine :)
  - andsoitis 2y ago
    > evolution is overrated: tardigrades are still doing fine :) The evolution of tardigrades as super fascinating: https://eartharchives.org/articles/tardigrade-genome-reveals-secrets-of-their-toughness-and-evolution/index.html https://eartharchives.org/articles/tardigrade-genome-reveals...
- 7thaccount 2y ago
  Chuck gave up doing Forth in assembly for modern processors a number of years ago, but developed the GreenArrays chips that are apparently like 144 computers on a chip. He programs that in some version of ColorForth and has done several talks on it. I have no clue if there is any value because I can't understand it's use case. It is really cool though that when he builds an application, he typically understands everything from the machine level all the way through the software and he designs them both to some kind of optimal overall system. He's got to be one of the only people alive who can still claim that I'd guess.
  - chuckadams 2y ago
larsbrinkhoff 2y ago
Tradition has it that the thing to do with Forth is implement your own toy and then call it a day. Usually not having learned how to actually program in Forth. Yes I'm bitter.
JBits 2y ago
If you're looking for something to do in Lua, I suggest making a game with the Love2D framework [love2d.org]!
- bmitc 2y ago
  I've had my eye on it for sure!

thefaux 2y ago

Lua and Forth is like pb&j.

mjevans 2y ago

It'd be interesting to see how compact the binary form is, and what external dependencies it has. Forth's selling points are mostly how compact a minimal environment can be, and how easy it is to extend that environment to do more useful things. The 'shell' is the compiler.

rasur 2y ago

I 'learned' Forth decades ago (on a Sinclair ZX81, so essentially a quite horrible experience), and tripped over it again recently.. ending up ploughing through the books "Thinking Forth" and (currently) "Starting Forth" both of which are extremely interesting and so very very different to what we use these days. It very much fits into that saying "A language that doesn't change how your think about programming, isn't worth knowing". I realise now just how shallow an understanding of Forth I had as a teen, back in the day ;) But I think the win here - these days - for Forth is in things like "running on small embedded devices".. I'm looking with interest at some of the activity around say Arduinos and am thinking that Forth is a rather nice fit for that sort of system. Have bought a kit, and am looking forwards to some non-work quality time to play further :) (The Books I meantion can be found online very easily, but you'll forgive them for being written back in a time when systems were _simpler_ to grok ;) )

_0ffh 2y ago
> I think the win here - these days - for Forth is in things like "running on small embedded devices" In principle that's not a bad idea, it's just that you're at least 40 years late to the party. FORTH was and propably is used in embedded systems for most of it's existence. Often simply with a minimal text console over UART, that being your "way in". Once you've got that going you can start builing up your system from the inside.
- rasur 2y ago
  Being late to the party is the story of my life, but fwiw, I was aware that FORTH was used a lot in this kind of use-case ;)
rwmj 2y ago
Artic Forth? I had a lot of fun with that. https://worldofspectrum.net/item/0031896/ https://worldofspectrum.net/item/0031896/
- rasur 2y ago
  I think it was, actually, yes. Thanks for the reminder!

RetroTechie 2y ago

Trying to get an overview of which languages allow for tiny implementations of their core features. Like, max. ~10KB binary size (but preferably a few KB's). This is assuming basic IO is trivial, like reading/writing to some memory location to get/print a character on text console. Forth is an obvious one. Basic another. There's some tiny Lisps out there. And Tcl. Any other languages that go that small?

giraffe_lady 2y ago
One thing you quickly run into with this exercise is needing to establish the boundaries around "programming language" which can be kind of fraught. For example miniKanren is tiny and is used as a DSL, but is capable of expressing any computation so does that count? Some type systems are turing complete and a naive implementation could be tiny. Is conway's game of life a programming language. You could probably strip a bunch of useful stuff out of sqlite's sql parser and get it below 10k. etc.
- samatman 2y ago
  You have to draw a line somewhere, and it's necessarily somewhat arbitrary. Mine is the size of the runtime, usually. So the Forth is the size of Lua + the 40 line script, minKanren is the size of the .scm file + the Scheme implementation, and so on. This ignores the host environment, which I think is fair: generally these will be enormously larger than they would actually have to be to support the language. I do award subjective bonus points to languages which actually have a freestanding runtime, that is, I could actually compile them and run them on a bare chip. Even then, I don't count the microcode which implements the instruction set of that chip, or the Verilog/VHDL which is needed to tape it out. Usually! ColorForth on GreenArrays gets even more bonus points, because not only is the language exceedingly compact, and freestanding, but the VLSI tool used to create the chip is also tiny to an almost unbelievable degree. So it wins some kind of prize in the special "total system complexity" category.
  - RetroTechie 2y ago
    > I do award subjective bonus points to languages which actually have a freestanding runtime, that is, I could actually compile them and run them on a bare chip. That's what I was getting at with "trivial IO": when you ignore what's needed to get data in/out, and optional parts of a standard library (if included), how big is the remainder, the implementation of the language constructs? (Potentially) standalone, self-hosting & small is indeed the bonus points I'm looking for. A tiny Basic or Forth running bare metal on a uC could be it. A 'tiny' language implemented using a multi-MB VM is not.

pjmlp 2y ago

While a great exercise and kudos to the author, I think languages like Forth and Lisp are much cooler to bootstrap from Assembly. Anyway, thanks for sharing.

samatman 2y ago
Assembly? Hah! It only counts if you use a magnetic needle and a very steady hand.
- pjmlp 2y ago
  From that point, first we need to mold some gears.

zelphirkalt 2y ago

Is there any Forth, that properly handles unicode strings, by which I mean, that it has sensible string length, substring and such functions or some standard library that has them? Basically all the usual stuff one needs. I tried to use GForth a while ago, but how to use strings properly was a mystery. I don't want to have to code all string functionality myself. Well, neither do I know how, nor do I want to. I guess I would have to study other languages' implementations and some standard documents or so for that, when actually I am doing another project. A gigantic rabbithole that would be. Afaik there is more planned in the 1.0 release of GForth. Reading line after line from a file was also difficult. I could not figure out, how to clear the storage used for the previous line properly. When I read a shorter line after a longer line, the storage would still contain the longer part of the longer line after the content of the shorter line. Perhaps there is a Forth that makes this easy? But it also needs to support that library, FFL, so that I have useful data types, and don't need to roll my own arrays or something ... Maybe my design philosophy is fundamentally different from what is needed for Forth?