README.md

go-go-monkey-repl

This is my implementation of the "monkey" langugue interpreter. I made this by following along the wonderful book Writing an Interpreter in Go by Thorsten Ball. I made a few extentions of my own after finishing, but the bulk of the credit goes to him!

I may play keep playing around with this, but know that it is a toy language, and you should not expect any kind of support if you choose to use it for anything. Though, it is licensed under MIT so there's nothing stoping you from doing that, other than the knowledge that you'll be on your own.

You can run the repl and play aound with it by running go run main.go. You can exit the repl by typing entering quit (one of my few extentions) or by just killing the process with Ctrl+C on linux.

Most of the modules come with tests you can run like so:

go test ./eval

Other than that, there's not that much to say, other than thank you the Thorsten! I had an amazing time reading the book and I highly recommend you do so too.

Not so FAQ

• Q: Why is it called go-go-monkey-repl
• A: I was originally going to just call it "the Go Monkey Repl" since it is a REPL for the Moneky language, written in go, and I intend to write the same in other languages too as an exercise for myself. Then I thought go-go would be a funny inspector Gadget joke.

Extentions

• 2023-09-18: ability to gracefully exit the repl with the quit command.
• 2023-09-18: iter builtin function. It gives you an array containing the individual characters when called on a string, and an array with the keys when called on a hash (dictionary). It just returns arrays since loops arent's implemented yet (though I plan to implement at least one) and you can faux iterate over arrays using the builtin first function.
• 2023-09-18: Add implementation for while loops. :D

ideas

Some ideas I might like to implement some day for fun:

• [] press up in repl to prefill last command
• [] allow multiline expressions in repl with use of \
• allow reading of monkey script files

A note on copying.

It's entirely possible you're looking at this repo with the goal of determining how capabale as a dev I am, and am thus worried how much of the code I simply coppied into a repo to seem impressive, and how much of it I actually understand.

As a general philosphy I ended up sicking to one rule of thumb: implementation I type out myself, tests I copy. I started out also typing out the testing, but after the first couple of times of extensive debugging due to simple typos I decided to just starty copying those. Go is also rather boilerplate-y/somewhat repetitive which got old quickly.

However, I did read through the book, and understand around 80-90% in there. As for evidence: First of all, you can just diff the my code against the canonical ones that are provided with the book and see that some of my implementations are in slightly different locations. But more importantly, I implemented a builtin function (iter) and a while construct, neither of which are in the book. That means that I have to understand at least something of what's going on ;)