Following the Z80 simulator in Scala (https://github.com/krzys9876/z80_sim_scala), this is a MS Basic interpreter to run similar programs. As always it's mostly for fun and for practicing FP, immutability, class composition and parser combinators.

I did not intend to implement all Basic commands - the list is quite long but I realised that actually most of my example programs use just a small portion of all available statements. So I chose the core: printing, loop, jumps, conditionals.

My implementation is not strict, e.g. I did not put constraints on numbers, string length, printing is a little different too bit overall the programs do what they are intended to. I did not implement string operations at all as I hardly use them in Basic.

I've spent quite some time on parser combinators, learning and browsing for simple solutions. I tried hard not to create a huge one-class-to-parse-them-all. This is where scala traits shine - they allow separating logical bits from one another yet combining them seamlessly (just be aware of circular dependencies).

This is enough to run tic-tac-toe (10x10) game, which was a test program for Z80 simulator.

I was wondering how to enable parameterized program execution, i.e. how to easily choose between executing e.g. first X steps or finishing after Y seconds etc.

I came up with the idea of Iterator and Iterable classes (I know, the names are so general that they may be easily confused...). Iterator simply runs a step method of a Iterable object and checks if the execution is over by invoking an external function. Is it an overkill for this purpose? Well, it may be but this is also a brain-teaser, and that's what fun projects are all about 😄

This also enables different execution of test (i.e. always run a test program to an end and check the results) vs runtime.