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BASIC parsing difficulties in EndBASIC

The original BASIC parser in EndBASIC 0.1 was very rudimentary and it stayed pretty much unmodified until the 0.10 release last month. This release brought major changes to the parser to support new features, but it wasn’t easy to implement them. In this post, I want to look into various difficulties that arose implementing certain BASIC constructs in EndBASIC. Overcoming these difficulties was difficult, but it was also fascinating because it gave me a glimpse of the design choices that the original BASIC designers must have faced. Capturing these ah-ha moments in a post is also tricky, but I’ll try anyway.

EndBASIC 0.10: Core language, evolved

After three months of early-morning hacking, I’m pleased to announce that EndBASIC 0.10 is now available—right on time for some holiday-time experimentation!

This release marks a huge milestone because it makes the language usable for real-world development.

You see, when I started this project over two years ago, I wrote a rudimentary interpreter for something that resembled BASIC and then launched EndBASIC 0.1. Since then, I have been piling onto those insufficient foundations by adding flashy features such as a web interface, a cloud file sharing service, and a hybrid text/graphics console. These features have been well-received in every demo I’ve given but… the feedback that always came back was the same: “Give me some sort of functions or subroutines!”, or “This is no BASIC without GOTO!”.

And these criticisms were right. Trying to write any sort of non-trivial program in EndBASIC was a daunting and frustrating experience. I had tried to simplify coding to the foundations of structured programming, but without a way to perform unstructured jumps (aka go-tos) or define custom functions… it was impossible to factor out common code, which is a need for the vast majority of programs that exceed a screenful of text. There were also usability deficits such as the lack of line numbers in error messages, which made it incredibly difficult to debug any failing program.

The situation had to change, and change it has in EndBASIC 0.10.

From AST to bytecode execution in EndBASIC

Since its inception two years ago, the EndBASIC interpreter has been using an AST-based execution engine. And during all this time, people have mocked the language for not allowing 10 GOTO 10. Well, fear not: the upcoming 0.10 release has full support for GOTO and GOSUB, features that were made possible by moving to a bytecode-based interpreter. Let’s take a peek at what the problems were and how I addressed them.

EndBASIC 0.9: Run shared demos easily

It is with great pleasure that I announce the release of EndBASIC 0.9.0 😎️.

The major feature in this new release is the ability to launch publicly-shared files via a click of a URL without having to create an account first. Here, try running my jmmv/bounce.bas or jmmv/paint.bas demos in your browser, now!

EndBASIC 0.8: Now, with graphics!

Graphics support has finally landed in EndBASIC and, with that, the 0.8 release is finally here.

This release marks a huge milestone in the development of EndBASIC. Supporting graphics is something I’ve had in mind since the very beginning but had been procrastinating on until a couple of months ago. I feared everything that would be involved in delivering this feature, and to be fair, I was right: getting the desktop console to work on all platforms, and especially getting it to work in CI for automated testing, was tedious. But it’s done now.