[Coco] Color Basic Renumber

[William Astle]

On 15-01-27 02:29 PM, Allen Huffman wrote:
> Nick, do you know much about the BASIC tokenizer format? It would be trivial to write a renumber program as an exercise. You would have to do some parsing but there is a small number of tokens that could have line numbers after them. It might be as simple as starting at a line, scanning through and stopping at each potential token to see if a line number is after it. By making as list, it would be easy to renumber.

That's essentially what the RENUM does. It doesn't notice all possible 
tokens that take line numbers (notably the ones that don't generally get 
used in programs like DEL). The critical tokens to consider are GOTO, 
GOSUB, THEN, and ELSE. You might also want to consider LIST, RUN, and 
DEL. You don't have to consider "ON" directly since it always has GOTO 
or GOSUB - just make sure to handle a comma separated list of line 
numbers after GOTO/GOSUB.

What RENUM actually does is make two passes. The first pass expands all 
line numbers out to 5 bytes and converts the numbers to a temporary 
representation with some notes. The second pass replaces all replaced 
line numbers with their new numbers and then collapse the resulting 
numbers back down to the smallest number of digits.

The actual code is a bit of a brain buster to understand.

The upshot is that it isn't quite as simple as it looks if you're going 
to do it in assembly, especially if you need to minimize the memory 
footprint.