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Put this in my "watch later" queue. I'm very interested in a Lisp whose type system is on par with that of Haskell/Ocaml. EDIT: Especially since Shen is now BS

Put this in my "watch later" queue. I'm very interested in a Lisp whose type system is on par with that of Haskell/Ocaml. EDIT: Especially since Shen is now BSD licensed.

AnimalMuppet 12y ago
To me, it seems impossible to have both macros and a type system on par with Haskell. Either your macros can no longer do arbitrary textural transformations, or your type system can't reason about macro cases. (Or, I suppose, your type system has to run after the macro transformations, and you could get a type error then just like you could get a syntax error then. But that means your IDE/development environment can't give you any type assistance on macro calls - you have to compile it to find out if it works. (Or, I suppose, your IDE has to run the macro for you and then do the type checking on the resulting post-macro code.)) I am open to being proven wrong, though...
- doublec 12y ago
  ATS had macros: http://ats-lang.sourceforge.net/htdocs-old/TUTORIAL/contents/macros.html http://ats-lang.sourceforge.net/htdocs-old/TUTORIAL/contents... I'm not sure if these made it into ATS2 though.
- necubi 12y ago
  Scala has macros [0], and as you reasoned the type checker has to run after the macro expansion. That's not a huge downside; to the user it still appears to be a single pipeline (parsing -> macro expansion -> type checking -> compilation). Haskell also has very powerful metaprogramming facilities, like template haskell [1]. [0] http://scalamacros.org/ http://scalamacros.org/ [1] https://wiki.haskell.org/Template_Haskell https://wiki.haskell.org/Template_Haskell
- sordina 12y ago
  > it seems impossible to have both macros and a type system on par with Haskell You should check out the work being done on typed template Haskell then.
- andrewchambers 12y ago
  You can have a language which has to be parsed top down, then you can have both complete type info, and arbitrary macros.
- deech 12y ago
  The second half of the talk (http://www.youtube.com/watch?v=lMcRBdSdO_U&t=17m30s http://www.youtube.com/watch?v=lMcRBdSdO_U&t=17m30s) is about turning a JSON object into a type using macros and meta-programming.
- gmfawcett 12y ago
  MetaOcaml's type-safe staged metaprogramming is not strictly a macro system, but it is morally equivalent: http://okmij.org/ftp/ML/MetaOCaml.html http://okmij.org/ftp/ML/MetaOCaml.html
616c 12y ago
Now, I understand that is BSD licensed, but I am bothered by their proud "we support OSI, but never GPL" attitude. I wonder what happened to the original developer, but does anyone know why he has GPL issues? Yes, I know he is not unique in the industry at large, but I rarely see project download pages with GPL with a red line through it. http://www.shenlanguage.org/download_form.html http://www.shenlanguage.org/download_form.html
- doublec 12y ago
  The original developers thoughts on GPL have been discussed at length on the Shen mailing list during the BSD licensing donation period. If you look through the archives you'll be able to read their thoughts. This link may be a start: https://groups.google.com/d/msg/qilang/mVSJIyp-OhM/FjcAOAWUio0J https://groups.google.com/d/msg/qilang/mVSJIyp-OhM/FjcAOAWUi... It's unfortunate that the original authors views on licensing takes so much discussion away from Shen itself as it's an interesting language.
  - 616c 12y ago
    So true. I am watching this video and I am very impressed. I am a novice programmer, but from what I read on HN the Shen system hits all cylinders a lot of the more powerful advanced programming paradigms. I am a Shen outsider and there seems to be some much overhead that is not technical when I read about it and it upsets me bc, well, it is a work of art. I just started studying Java, and found the yet to be certified Java implementation. I am afraid to look at it, lest brains come of my nose. https://github.com/hraberg/Shen.java https://github.com/hraberg/Shen.java
    - tluyben2 12y ago
      One of the great advantages of Shen is that it is built on top of a very simple Lisp called KL of which you can (at least basically working) implement an interpreter or compiler in any language in a day. And when you did that, Shen will run on it. That's why there are so many targets and that's why most targets are not mature. I find it a great advantage though; you can make a compiler or runtime embedded in whatever you are doing really fast and then optimise it as you go. Edit: I would say, if you want to practice on implementing a compiler & runtime (or VM with JIT or LLVM frontend etc) KL is a good place to start. It's so easy (again, to get something working; to optimise etc is obviously just as painful as with any other language implementation) that it is a lot of fun and you learn a lot if you never did it before.

Put this in my "watch later" queue. I'm very interested in a Lisp whose type system is on par with that of Haskell/Ocaml. EDIT: Especially since Shen is now BSD licensed.

AnimalMuppet 12y ago

To me, it seems impossible to have both macros and a type system on par with Haskell. Either your macros can no longer do arbitrary textural transformations, or your type system can't reason about macro cases. (Or, I suppose, your type system has to run after the macro transformations, and you could get a type error then just like you could get a syntax error then. But that means your IDE/development environment can't give you any type assistance on macro calls - you have to compile it to find out if it works. (Or, I suppose, your IDE has to run the macro for you and then do the type checking on the resulting post-macro code.)) I am open to being proven wrong, though...

doublec 12y ago
ATS had macros: http://ats-lang.sourceforge.net/htdocs-old/TUTORIAL/contents/macros.html http://ats-lang.sourceforge.net/htdocs-old/TUTORIAL/contents... I'm not sure if these made it into ATS2 though.
necubi 12y ago
Scala has macros [0], and as you reasoned the type checker has to run after the macro expansion. That's not a huge downside; to the user it still appears to be a single pipeline (parsing -> macro expansion -> type checking -> compilation). Haskell also has very powerful metaprogramming facilities, like template haskell [1]. [0] http://scalamacros.org/ http://scalamacros.org/ [1] https://wiki.haskell.org/Template_Haskell https://wiki.haskell.org/Template_Haskell
sordina 12y ago
> it seems impossible to have both macros and a type system on par with Haskell You should check out the work being done on typed template Haskell then.
andrewchambers 12y ago
You can have a language which has to be parsed top down, then you can have both complete type info, and arbitrary macros.
deech 12y ago
The second half of the talk (http://www.youtube.com/watch?v=lMcRBdSdO_U&t=17m30s http://www.youtube.com/watch?v=lMcRBdSdO_U&t=17m30s) is about turning a JSON object into a type using macros and meta-programming.
gmfawcett 12y ago
MetaOcaml's type-safe staged metaprogramming is not strictly a macro system, but it is morally equivalent: http://okmij.org/ftp/ML/MetaOCaml.html http://okmij.org/ftp/ML/MetaOCaml.html

616c 12y ago

Now, I understand that is BSD licensed, but I am bothered by their proud "we support OSI, but never GPL" attitude. I wonder what happened to the original developer, but does anyone know why he has GPL issues? Yes, I know he is not unique in the industry at large, but I rarely see project download pages with GPL with a red line through it. http://www.shenlanguage.org/download_form.html http://www.shenlanguage.org/download_form.html

doublec 12y ago
The original developers thoughts on GPL have been discussed at length on the Shen mailing list during the BSD licensing donation period. If you look through the archives you'll be able to read their thoughts. This link may be a start: https://groups.google.com/d/msg/qilang/mVSJIyp-OhM/FjcAOAWUio0J https://groups.google.com/d/msg/qilang/mVSJIyp-OhM/FjcAOAWUi... It's unfortunate that the original authors views on licensing takes so much discussion away from Shen itself as it's an interesting language.
- 616c 12y ago
  So true. I am watching this video and I am very impressed. I am a novice programmer, but from what I read on HN the Shen system hits all cylinders a lot of the more powerful advanced programming paradigms. I am a Shen outsider and there seems to be some much overhead that is not technical when I read about it and it upsets me bc, well, it is a work of art. I just started studying Java, and found the yet to be certified Java implementation. I am afraid to look at it, lest brains come of my nose. https://github.com/hraberg/Shen.java https://github.com/hraberg/Shen.java
  - tluyben2 12y ago
    One of the great advantages of Shen is that it is built on top of a very simple Lisp called KL of which you can (at least basically working) implement an interpreter or compiler in any language in a day. And when you did that, Shen will run on it. That's why there are so many targets and that's why most targets are not mature. I find it a great advantage though; you can make a compiler or runtime embedded in whatever you are doing really fast and then optimise it as you go. Edit: I would say, if you want to practice on implementing a compiler & runtime (or VM with JIT or LLVM frontend etc) KL is a good place to start. It's so easy (again, to get something working; to optimise etc is obviously just as painful as with any other language implementation) that it is a lot of fun and you learn a lot if you never did it before.