[Info-vax] BASIC and AST routines

[Simon Clubley]

On 2021-11-19, Dave Froble <davef at tsoft-inc.com> wrote:
>
> I'm going to confess to curiosity.  Why are R0, R1, SP, and PC passed to an AST 
> routine?
>

Because it's another example of VMS functionality being implemented
at way too low an abstraction level because of the need to support
Macro-32 as an application programming language.

In a modern version of VMS, that would be hidden from the application
programmer as an implementation detail and the most you would have to
do would be to tag the AST routine with a pragma or some type of __ast__
attribute that the compiler understood and then automatically generated
the right code for you.

Simon.

-- 
Simon Clubley, clubley at remove_me.eisner.decus.org-Earth.UFP
Walking destinations on a map are further away than they appear.