[Info-vax] BASIC and AST routines

[Craig A. Berry]

On 11/17/21 5:14 PM, 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.

There is an example in the docs here:

<https://docs.vmssoftware.com/vsi-openvms-rtl-screen-management-smg-manual/#_5935disable_broadcast_trapping>

of calling SMG$ENABLE_UNSOLICITED_INPUT.  The example does not work
as-is on post-Alpha architectures -- you have to declare the AST
routines as FUNCTION INTEGER and not SUB.  But as far as parameter
passing, if memory serves, what it does works.