Discussion
Trying to think what is worth doing.
- start reading the BASIC code for the nibble magazine word processors
- have another attempt at writing a Tiny BASIC interpreter
(On this point I have decided to 'muddle through', and just make up the memory structure as I go along).
- should really start zine number 2, SKETCH.BAS
- polish and finish off BAGQUEST
- explore more BBC Micro BASIC
- Load Stefan's BASIC back onto the ESP32
- remember to look at the CH32 board I brought
Have also had some discussions in direct messages about how to go about writing Dandelion BASIC, the Tiny BASIC I am developing for the people's permacomputer project.
The various methods I know about are:
- Intermediate Language method
- tokenised method
- direct interpretation
It seems from exploration, research, and a bit of tinkering that it may be simpler to merely directly interpret the BASIC code.
That is, we do not add any other layers of abstraction into the interpreter.
@dirtycommo Personally I just tokenize BASIC into an AST, and interpreter runs off those. I don't like char-by-char tokenizing every single time.
I'm still being lazy in mine, I should translate expressions into RPN with operator precedence, and then rewrite them as algebraic on LIST, but I don't.
@mdhughes can you help me a little bit with this?
Do you have a good link to something I can look at to understand where I am going with this?
So far I am trying to figure out how to structure the memory, and then learn the syntax of the gcc AVR assembler.
Tokenising has a good example in BBC Micro Basic and... A few others?
@dirtycommo What I learned the most from was the Atari Basic Source Book:
https://archive.org/details/ataribooks-the-atari-basic-source-book
It's pretty dense 6502 ASM, but has a lot of explanations of the algorithms.
The other was The Dragon Book:
https://archive.org/details/compilersprincip0000ahoa
(been copyrighted offa Archive, but our friend Anna or other places will have it)
Which is more how I work, high-level lang compiler, make an AST, Aho et al. go on to compile to machine code, which I don't bother with, but you will.
I think the problem I am having is the assembler directives for avrdude and gcc.
You have .section headers, then text, then something called .bss directives... It's quite complicated.
I have a general understanding of the memory map of the atmega2560, but what I don't understand is how to use these assembler directives to put the code into flash or RAM.
I understand that there is some automatic process to this (linking?) in gcc?
Does anyone have any good resources?
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