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Lisp languages should be great for embedding into games to implement game logic, instead of more straightforward solutions such as embedding Lua. I've always wa

Lisp languages should be great for embedding into games to implement game logic, instead of more straightforward solutions such as embedding Lua. I've always wanted to explore this for my iOS side-project game, which now uses an event-based system inspired by ReactiveX, implemented in Lua. This works pretty well but is very hard to debug. The main thing holding me back to try to replace it with something Lisp-like is that I have zero experience in Lisp programming. I know some FP theory (in fact the Lua-based event system lends some concepts from it), but when I try to reason about common subproblems I really have no idea how to map them to something like Lisp. For example how to efficiently implement a message bus with observers that can register themselves, using state-based functions to execute when certain events are received, scheduling events, async/await to suspend processing until some event is received, etc. Does anyone have pointers to books or websites to learn 'real-world' LISP programming? In other words not yet another introduction that shows the same old forced examples that just show you how to evaluate an expression or use higher-order functions to solve artificial toy problems, but resources that teach you how to be productive in a Lisp language?

phoe-krk 6y ago
> but when I try to reason about common subproblems I really have no idea how to map them to something like Lisp. For example how to efficiently implement a message bus with observers that can register for certain events. I think that's a badly posed question. The main benefits of using Lisp are its introspection and interactivity. You can use the REPL to inspect your message bus at runtime, you can modify parts of it as it runs, you can interactively debug errors as they happen, but none of that is directly related to "how to implement a message bus". I think that is more of an ADS question that it is a Lisp question; an efficient message bus, no matter whether you implement it in Lisp or in C or in Haskell, needs some synchronization primitives from the programming language core that are likely backed by OS primitives, as well as some data structures that need to be cleverly designed to be fast. Neither of these is language-specific - only means of implementing and using those might be language-specific. In other words: Lisp makes it possible to be more productive by means of dramatically reducing the time of feedback loop and by means of providing in-depth language introspection, but it doesn't solve the problem of actually needing to figure out how to design programs and data structures. That's why e.g. SICP is not a Scheme tutorial, despite using Scheme throughout the whole book.
- pjc50 6y ago
  This is a very classic Lisp answer in that "productivity" is considered in the pure abstract, and that the specific question of how to do a specific thing - the actual productive result - is uninteresting. Who would expect the classic book on Scheme to teach you how to write Scheme programs?
  - phoe-krk 6y ago
    SICP isn't a book on Scheme. It is not a Scheme tutorial; it uses Scheme to teach programming. One can learn Scheme by following the book and inferring everything that is done in there, but the topic of the book isn't teaching Scheme, it's teaching programming.
  - phoe-krk 6y ago
    Regarding productivity, I don't consider it abstract. I feel a concrete efficiency boost from the two things I mentioned, which are interactive and incremental development with a very short feedback loop (no time wasted while waiting for the toolchain to do its work) and the ability to introspect and debug the live system (since I do not need to bother with external debugger and tooling). What exactly do you mean by "uninteresting"?
    - pjc50 6y ago
      The original post complains of not knowing how to solve their particular problem in Lisp, and gives an example: > how to efficiently implement a message bus with observers You say: > I think that's a badly posed question But it isn't! It's the specific thing that person is trying to do and is having trouble with, the act of translating structures and designs they understand from other languages into the Lisp language. This is the barrier to Lisp adoption. You can cite iterative development and live debugging all you want, but they only benefit after you've actually written a program, which is the barrier the potential users are struggling at.
      - phoe-krk 6y ago
        > but they only benefit after you've actually written a program, which is the barrier the potential users are struggling at No, you miss the point. There is little benefit in interactive and incremental development once a program is written. The very benefit that this such incrementality provides is noticeable during the process of writing the program, not after it; when a program is written, it's written, and from some point it doesn't really matter if you've done it by mutating an image-based programming language or by linking together compiled C objects.
mlatu 6y ago
I liked the book Practical Common Lisp (PCL) very much, you can read it online for free on the authors website: http://www.gigamonkeys.com/book/ http://www.gigamonkeys.com/book/ I suggest using portacle (a preconfigured emacs) as development environment during that course as this is the easiest way to get cracking in CL imho. Although Janet's core library is different from CL, I think once you grok LISP, it's not hard to switch to another dialect: After working through ~half of PCL I abandoned it in favour of a learning-by-doing approach in ClojureCLR as I work mostly in .NET or Mono atm.
- w0utert 6y ago
  Great, I will check it out!
sahil-kang 6y ago
If you’re interested in Common Lisp, Practical Common Lisp is a good overview of the language [1]. Since you’ve done game programming, here’s a simple snake game I wrote a while back; you might find it useful to peruse the code [2]. You can find a couple of bigger libraries I wrote on my github if you’re interested in seeing more substantial code. [1] http://www.gigamonkeys.com/book/ http://www.gigamonkeys.com/book/ [2] https://github.com/SahilKang/cl-snake https://github.com/SahilKang/cl-snake
johannesgoslar 6y ago
There is Nu which runs on top of the Objective-C runtime: https://programming-nu.github.io/ https://programming-nu.github.io/ Relative easy to read code and has actually been used with some iOS games.
jonathanstrange 6y ago
The real power of Lisp becomes apparent when you develop programs top-down with very general data structures with their own accessors and a liberal use of higher-order functions. I still think that Winston & Horn's classic Lisp (3rd ed.) conveys these ideas very well. SICP is also very good at it, but it's based on Scheme.
thosakwe 6y ago
Learn GNU Guile, it's a dialect of Scheme. AFAIK, Scheme is specifically intended for use in teaching programming. I spent a late night reading the manual and hacking out some toy programs, and the rest is history. TLDR: Guile is very easy to learn
vindarel 6y ago
A great article on compile-time computing (with CL): https://medium.com/@MartinCracauer/a-gentle-introduction-to-compile-time-computing-part-3-scientific-units-8e41d8a727ca https://medium.com/@MartinCracauer/a-gentle-introduction-to-... There are good references and snippets on the Cookbook: https://lispcookbook.github.io/cl-cookbook/ https://lispcookbook.github.io/cl-cookbook/ for libraries, see https://github.com/CodyReichert/awesome-cl https://github.com/CodyReichert/awesome-cl (and see the lparallel or lfarm libraries, channels, cl-gserver, the built-in SBCL threading functions, etc) Also note that CL is not purely functional, you can throw in FP or OOP or iterative code.
flavio81 6y ago
>Does anyone have pointers to books or websites to learn 'real-world' LISP programming? https://lisp-lang.org/learn/getting-started/ https://lisp-lang.org/learn/getting-started/ You can start here to set up your IDE and then read the "Practical Common Lisp" book.

phoe-krk 6y ago

> but when I try to reason about common subproblems I really have no idea how to map them to something like Lisp. For example how to efficiently implement a message bus with observers that can register for certain events. I think that's a badly posed question. The main benefits of using Lisp are its introspection and interactivity. You can use the REPL to inspect your message bus at runtime, you can modify parts of it as it runs, you can interactively debug errors as they happen, but none of that is directly related to "how to implement a message bus". I think that is more of an ADS question that it is a Lisp question; an efficient message bus, no matter whether you implement it in Lisp or in C or in Haskell, needs some synchronization primitives from the programming language core that are likely backed by OS primitives, as well as some data structures that need to be cleverly designed to be fast. Neither of these is language-specific - only means of implementing and using those might be language-specific. In other words: Lisp makes it possible to be more productive by means of dramatically reducing the time of feedback loop and by means of providing in-depth language introspection, but it doesn't solve the problem of actually needing to figure out how to design programs and data structures. That's why e.g. SICP is not a Scheme tutorial, despite using Scheme throughout the whole book.

pjc50 6y ago
This is a very classic Lisp answer in that "productivity" is considered in the pure abstract, and that the specific question of how to do a specific thing - the actual productive result - is uninteresting. Who would expect the classic book on Scheme to teach you how to write Scheme programs?
- phoe-krk 6y ago
  SICP isn't a book on Scheme. It is not a Scheme tutorial; it uses Scheme to teach programming. One can learn Scheme by following the book and inferring everything that is done in there, but the topic of the book isn't teaching Scheme, it's teaching programming.
- phoe-krk 6y ago
  Regarding productivity, I don't consider it abstract. I feel a concrete efficiency boost from the two things I mentioned, which are interactive and incremental development with a very short feedback loop (no time wasted while waiting for the toolchain to do its work) and the ability to introspect and debug the live system (since I do not need to bother with external debugger and tooling). What exactly do you mean by "uninteresting"?
  - pjc50 6y ago
    The original post complains of not knowing how to solve their particular problem in Lisp, and gives an example: > how to efficiently implement a message bus with observers You say: > I think that's a badly posed question But it isn't! It's the specific thing that person is trying to do and is having trouble with, the act of translating structures and designs they understand from other languages into the Lisp language. This is the barrier to Lisp adoption. You can cite iterative development and live debugging all you want, but they only benefit after you've actually written a program, which is the barrier the potential users are struggling at.
    - phoe-krk 6y ago
      > but they only benefit after you've actually written a program, which is the barrier the potential users are struggling at No, you miss the point. There is little benefit in interactive and incremental development once a program is written. The very benefit that this such incrementality provides is noticeable during the process of writing the program, not after it; when a program is written, it's written, and from some point it doesn't really matter if you've done it by mutating an image-based programming language or by linking together compiled C objects.

mlatu 6y ago

I liked the book Practical Common Lisp (PCL) very much, you can read it online for free on the authors website: http://www.gigamonkeys.com/book/ http://www.gigamonkeys.com/book/ I suggest using portacle (a preconfigured emacs) as development environment during that course as this is the easiest way to get cracking in CL imho. Although Janet's core library is different from CL, I think once you grok LISP, it's not hard to switch to another dialect: After working through ~half of PCL I abandoned it in favour of a learning-by-doing approach in ClojureCLR as I work mostly in .NET or Mono atm.

w0utert 6y ago
Great, I will check it out!

sahil-kang 6y ago

If you’re interested in Common Lisp, Practical Common Lisp is a good overview of the language [1]. Since you’ve done game programming, here’s a simple snake game I wrote a while back; you might find it useful to peruse the code [2]. You can find a couple of bigger libraries I wrote on my github if you’re interested in seeing more substantial code. [1] http://www.gigamonkeys.com/book/ http://www.gigamonkeys.com/book/ [2] https://github.com/SahilKang/cl-snake https://github.com/SahilKang/cl-snake

johannesgoslar 6y ago

There is Nu which runs on top of the Objective-C runtime: https://programming-nu.github.io/ https://programming-nu.github.io/ Relative easy to read code and has actually been used with some iOS games.

jonathanstrange 6y ago

The real power of Lisp becomes apparent when you develop programs top-down with very general data structures with their own accessors and a liberal use of higher-order functions. I still think that Winston & Horn's classic Lisp (3rd ed.) conveys these ideas very well. SICP is also very good at it, but it's based on Scheme.

thosakwe 6y ago

Learn GNU Guile, it's a dialect of Scheme. AFAIK, Scheme is specifically intended for use in teaching programming. I spent a late night reading the manual and hacking out some toy programs, and the rest is history. TLDR: Guile is very easy to learn

vindarel 6y ago

A great article on compile-time computing (with CL): https://medium.com/@MartinCracauer/a-gentle-introduction-to-compile-time-computing-part-3-scientific-units-8e41d8a727ca https://medium.com/@MartinCracauer/a-gentle-introduction-to-... There are good references and snippets on the Cookbook: https://lispcookbook.github.io/cl-cookbook/ https://lispcookbook.github.io/cl-cookbook/ for libraries, see https://github.com/CodyReichert/awesome-cl https://github.com/CodyReichert/awesome-cl (and see the lparallel or lfarm libraries, channels, cl-gserver, the built-in SBCL threading functions, etc) Also note that CL is not purely functional, you can throw in FP or OOP or iterative code.

flavio81 6y ago

>Does anyone have pointers to books or websites to learn 'real-world' LISP programming? https://lisp-lang.org/learn/getting-started/ https://lisp-lang.org/learn/getting-started/ You can start here to set up your IDE and then read the "Practical Common Lisp" book.