Jasic: A Complete Interpreter in One Java File

July 18, 2010 code jasic language parsing

Update 2011/09/9: Moved JASIC from bitbucket to github.

I just put the finishing touches on a tiny little interpreter project: Jasic. Jasic is a dialect of the original BASIC programming language. It lacks functions and scope, but it’s a usable language. Even on an old Apple IIe, it was powerful enough to get me hooked on coding for life. Also, you can draw a Mandelbrot set with it.

I wanted to see if I could fit a complete interpreter in a single readable Java file. It worked out better than expected, so I went ahead and cleaned up the code and commented the hell out of it. If you’ve always wanted to learn more about interpreters, now you’ve got a little primer.

Here’s a little code to give you a flavor of the language:

' Initialize the loop counter.
count = 10

' Stop looping if we're done.
if count = 0 then end
print "Hello, world!"

' Decrement and restart the loop.
count = count - 1
goto top

Old school! All of the code is right here in Jasic.java. There’s also a README to help get you started. What are you waiting for?