Racket Compiler and Runtime Status

Jesse Alama here. If you bought a book from me but are unsatisfied, I'm happy to refund you. If you found my stuff unhelpful, let me know what's missing and I can try to include a discussion of that in the next edition. Just write me offline. Or write to the group, or visit us (or me) in the Racket Slack.

I wrote my stuff to help people get into web development with Racket. I love web devel, and Racket, too. You and I have a lot in common: I found the official docs puzzling, so I worked out my own approach to them and made _Server: Racket_. It should go without saying that that's the origin story of just about every paid book out there on applications of programming language X to domain Y. That's not even a criticism of the Racket docs. Plenty of tools/languages also have good docs, and there are lots of books, too. How many Django books (or even courses) are out there?

There are also some great web programming tutorials out there for Racket, too. I recommend this one, by Racket star Jens Axel Søgaard: https://github.com/soegaard/web-tutorial .

I hope you'd give Racket a chance. Since you're talking about it, it sounds like you're dipping your toes in the waters. I'm pretty sure you'll find them quite welcoming. That said, all this negativity is pretty off-putting.

It is a very multi-dimensional issue. While all these languages belong to the same family, they also take some time to learn, and each has its specific strengths. It is probably very helpful to think about what matters most to you, and pick what matches your needs best for the first language.

Here some axes of distinction:

1. supported programming styles

2. support for concurrency

3. performance of generated code and parallelism

4. floating-point performance

5. level of standardization

6. closeness to the system and capability to call into C functions, or functions with C ABI

7. suitability for scripting and stand-alone programs

8. GUI programming

9. Comprehensiveness and beginner-friendliness of documentation

10. REPL Programming

11. Libraries

12. Licenses

Here what I know about the languages you name:

(I also mention ABCL = Armed Bear Common Lisp a few times, just to illustrate that you also can run Common Lisp on the Java Platform).

1. supported paradigms - Clojure is very opiniated in supporting and demanding a purely functional style. It uses purely functional data structures. Racket and Scheme support a functional style well, but allow for seamless imperative code. Common Lisp is agnostic, one can program in a purely functional way and there are libraries with purely functional data structures, but it requires much more discipline.

2. Clojure has best support for concurrency and server-like tasks, it is made for that. Racket also supports green threads, apart from its places parallelism.

3. Racket, Chez, Common Lisp and so on support OS level threads and parallelism. Chez and Common Lisp stand out as they generate the most performant code - when it comes to raw computing power, single-threaded SBCL code will be faster than multi-threaded Clojure code. SBCL, for example, also allows to add compiler hints which generate unsafe code with better optimizations (for example, indicating that integer values will only be in a specific range).

4. SBCL has by far the best floating-point performance, I think Chez comes after that, and I'd expect Racket to improve further here. Racket has also been reviewed very favourably for scientific applications (https://khinsen.wordpress.com/2014/05/10/exploring-racket/ - Konrad Hinsen, the author, was an early contributor to Numerical Python).

5. Of all these, Common Lisp is standardized most. Especially Racket and Clojure are defined by their implementation.

6. Clojure and ABCL allow to call into Java. In turn, all of Common Lisp, Guile, Racket, Chez allow to call easily into C. There is a performance difference, I think, between most Schemes and SBCL: Calling into a C function has some extra cost because the stack is handled differently (I think it is because of continuations). I also tried to call into Rust functions from Racket and that works very nicely.

7. Clojure's startup time is simply too slow for scripting. It is also a bit hampered in that it runs on the JVM. There is babashka, which is interesting but has no mature status. Conversely, Common Lisp and Racket are well suited to scripting. It is also possible to compile SBCL and Racket programs into a single executable. I think SBCL supports this case best, for running Racket programs, an extra runtime library or a standard Racket installation is needed. Guile is also well-suited to scripting and is closer to the OS than some other Lisps.

8. Racket has a very nice support for GUI programming with a platform-independent functional API. Clojure and ABCL also allow to call into Swing and Fx code written in Java. I have not tried the rest but it looks relatively painful and brittle in comparison.

9. Racket has very comprehensive and high-quality documentation good for beginners. Clojure is also comprehensively documented, but might assume a bit more experience. Common Lisp is, as an open system, more eclectic, and this might lead especially beginners to underestimate how mature and good it is. It is very under-hyped compared to Clojure. But there is the Common Lisp Cookbook on the web, which is really good. I can also warmly recommend the books "Practical Common Lisp" by Peter Seibel, and "Common Lisp Recipes" by (corrected!) Edmund Weitz. If you want to have true understanding, and are about to write industry-grade robust software, they are really worth every cent.

10. REPL Programming: Lisps and Schemes such as Racket have a subtle difference which affects the style of programming. In Lisp, everything is dynamic and you can re-load and evaluate parts of the program when it is running. This makes for a great development environment. In contrast to that, Racket for example has a clear distinction between compilation time and run time, which gives certain safety and correctness guarantees, but requires that the program is re-loaded more often during development.

11. Libraries: Racket has a distinct "Batteries included" feeling which makes it nice for beginners. Clojure uses Leiningen which runs on top of Maven to automatically retrieve libraries, it works very well. Racket has a similar system. Common Lisp is more eclectic again, what is used today is quicklisp and asdf (see the Common Lisp Cookbook). There is also a reasonable support in OS Packages e.g. in Debian, and in addition GNU Guix is a very interesting solution for packaging of Lisp libraries and in polyglot projects.

12. Licenses: Clojure has a non-copyleft license (Eclipse License) which might be an obstacle if you want to publish copyleft libraries and code (not sure about the exact limits here but the problem is that in a Lisp system, there is less clear of a boundary of system or language code and your own code, so it is probably advisable to use a language with compatible license if you want to publish copyleft code). Racket is Apache 2 which is GPL compatible. Guile is, as part of the GNU system, GNU LGPL.

In summary, I think Racket is great for beginners, although you could start with all of them. Clojure is fantastic for servers and to learn about functional programming. Guile and Racket are great for scripting. Common Lisp, and especially SBCL requires a bit more learning effort at the beginning, but it is a really mature and highly performant system which gives you a lot of freedom.

Go here for guidance: https://docs.racket-lang.org/getting-started/index.html

Check 'Getting started' above, but I'd suggest that if you are already a developer, start with the Racket Guide, and 'How to Program Racket: a Style Guide' both available in the documentation site https://docs.racket-lang.org (and bundled with the installer). The Racket Guide is fully integrated with the Reference - click on something and it will take you to the reference for the full definition.

It's also worth working through HTDP https://htdp.org - with the caveat that you are using the teaching languages. A really nice thing is Racket can support students/learners, without compromising the full language. The Racket installer includes Racket, proper, the teaching languages, and a number of other languages.

> Clojure uses Leiningen which runs on top of Maven to automatically retrieve libraries, it works very well.

In the same way, Common Lisp uses Quicklisp, which runs on top of ASDF to automatically retrieve and compile libraries. It works very well.