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Learning in the small

published 2014-04-22

Writing a Lisp

I like to learn new tools and concepts by experimenting with small projects whose sole purpose is to help me grasp something better. Working on a larger project in a team with other people is invaluable, but doing things on a smaller scale on my own offers a different perspective.

Having recently started to write a lot more C at work than I used to, I felt that it was a good idea to do a smaller project in the language. It turned out Build Your Own Lisp [1] came out just when I needed it, so I had a go at it [2].

I cannot recommend this book enough if you feel like you would enjoy building a dynamic language in C from scratch (using just a parser library). It is one of the best tutorial-style books I have ever read. It achieves a perfect balance between being didactic and leaving freedom to the user.

My Lisp ended up being different from the one described in the book in several minor ways. For instance: it has more types, builtins take expressions instead of values, values are based on a union (which saves memory), memory management works differently, the source more organized... In that respect the book delivers exactly what it promised: the reader is encouraged to build "his own" Lisp.

In the end I got just what I wanted from this experience: I clearly improved my C and had the satisfaction to write a working programming language in a few hours scattered over three weekends.

Oh, just in case you were wondering, nobody paid me to write that blog post!

1: http://www.buildyourownlisp.com/

2: https://github.com/catwell/ownlisp

Moving on to Go

Next, I will probably be learning Go [3]. Go is a weird language in that about half of the technical people I follow and look up to like it a lot, and the other half hates it. The latter tend to be users of languages with stricter type systems...

I have to admit that, if I had looked solely at the technical merits of both languages, I would probably have learned more Rust [4] instead. I already know some Rust, but not enough to use it productively. Its main advantages are its (arguably) better type system and the fact that it can run without a GC or a frontend, making it suitable to write dynamic libraries.

However, Rust doesn't look completely stable yet, whereas Go is already used in production by several serious companies. Also, I am a distributed systems programmer, and most [5] of [6] the [7] interesting [8] codebases [9] I see popping up around in that field are written in Go.

Moreover, Go appears to be a simpler language than Rust. I suspect I can learn enough of it to read code "fluently" and write some much faster. So Go it is, and Rust will probably be next.

3: https://gobyexample.com/

4: http://www.rust-lang.org/

5: https://perkeep.org

6: https://github.com/coreos/etcd

7: https://github.com/ha/doozerd

8: https://github.com/bitly/nsq

9: https://github.com/project-iris/iris