[Info-vax] BASIC and AST routines

[Jonathan]

On Wednesday, November 17, 2021 at 6:14:30 PM UTC-5, John Doppke wrote:
> So I've been playing with writing AST routines (stubbornly) in BASIC. They work ok, but I've found I have to declare the routine as having 5 'standard' parameters - "function long AST long (p1, p2, p3, p4, p5)". I'm not sure what the 5 parameters are, but doing anything with them is usually a bad idea. I communicate with my main program using common or event flags. 
> 
> Now I need an AST for a call that requires a parameter - SMG$ENABLE_UNSOLICITED_INPUT. I've tried adding a parameter in my usual list in different ways but I can't get it to work. Every time it's called I get a reserved opcode exception. (A DCLAST call with my AST works ok). 
> 
> Can anyone shed some light on what the parameters are that BASIC is getting? I'll probably end up writing this one in MACRO, but I want to understand what is happening. 

function long astRoutine by value(long pasteboard, astArgument, r0, r1, pc, psl)

should work, though how the first two args are passed is hard to determine; experiment with by ref.  As you say, messing with the final four args is prone to problems...