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Getting Started With Scheme

2018-06-16

I’ve just started to get my feet wet with Scheme. My reasons for learning Scheme descend from my desire to learn more about implementing interpreters and the fact that two books on this subject make use of Scheme for their examples. In case you’re wondering, the book that really led to me deciding it’s worthwhile to use Scheme is the book “Essentials of Programming Languages” (EOPL). The book I need to work through before that one is “Structure and Interpretation of Computer Programs” (SICP) which also uses Scheme.

Chances are if you’ve decided to learn Scheme or LISP it’s because you’re a curious programmer. I can’t imagine finding the book SICP on accident when looking around for a first book on programming, and if you did stumble upon it on your own, well I feel slightly bad for you. It definitely looks like a great book on learning about programming and computing, however, it is fairly far outside what most first programming books are on. SICP is not going to teach you how to make a website or a game. However, if you already know how to program and are looking to expand your horizons it looks like it has a lot to offer.

Since I have too much time on my hands and I’m generally a curious programmer, I’m going to work through SICP and then EOPL so that I can learn more about how interpreters and compilers work so that I can ultimately implement my own. I’ve always been interested in how compilers work, but it wasn’t until recently that I made it a point of actually learning. For a long time (and still to a big extent) they seemed to work magically. Then I did a little research and read “Writing an Interpreter in Go” by Thorsten Ball, and found that they are not magic. If you’re looking for a fast and good book that will help you write your first interpeter the book by Ball is a great start.

So I’m onto SICP and learning Scheme then.

The first thing I noticed is that learning Scheme will require using different tools then Visual Studio or other “mainstream” programming environments. While Scheme has a standard now, it’s clearly used more for academic purposes than for real world programming, and as such the toolset surrounding it is a little different. Getting started was confusing, especially since I basically just wanted to find a way to write Scheme that wouldn’t be too painful.

Luckily, there is a great tool which is cross-platform and free. It’s called DrRacket and it’s an IDE and interpreter for the Racket language, which is a Scheme/LISP variation. While the Racket language isn’t Scheme exactly, DrRacket, has a way of putting it into a mode which is compatible with the Scheme dialect used in both SICP and EOPL. The IDE is easy to use, and also includes a REPL (Read-Eval-Print-Loop). You can download DrRacket here. For how to set up DrRacket to work with SICP you can check out the guide here. DrRacket and the Racket language look to be interesting tools in their own right, as it’s an ecosystem for developing and deploying new languages.

Once you’ve got DrRacket setup and begin questioning whether or not you should actually learn Scheme because it won’t help you get a job, you’ll probably like me want to start learning how to do things in Scheme like you do in other languages. It’s a little different then how you would do stuff in a language like C# or Java. First, Scheme is a functional programming language, which in and of itself is basically totally different then C# and Java which are imperative programming languages.

The other thing you’ll most likely notice, or at least I seemed to notice, is that since there are lots of dialects of Scheme, LISP, and so on, it’s not exactly clear on what will work with the version you’ve chosen to work with.

I’ve decided to stick with the simple SICP mode that DrRacket has so that I hopefully don’t have to search for how to translate concepts and function names all the time while I’m working through SICP.

But I do feel that it’s important to write the canonical first program in Scheme similar to how just about every other book on programming does (SICP doesn’t). If you don’t know what that program is, then you may want to learn another language first. If not, and you already bought SICP and have no idea how to prograrm, follow the link for putting DrRacket in SICP mode write the following in the REPL (the window on the bottom that yells at you when you type things in it doesn’t like).

(display “hello world”)

And now you can say you program in Scheme.