On Wednesday 31 December 1969 19:00, Andrew Davie wrote:
> OK, I understand that request. Essentially you want a local-variable
> scope. I'll have a think about how this could/should be done. Perhaps
> there's a good way to do it with existing code, anyway (for eg: defining
> the sections in separate files, and only exporting symbols which should be
> global).
That's close to the idea... but with overlays you may end up sharing
identifiers across many subroutines that are scattered throughout your code.
Since you sometimes have to put routines in certain spots, like the start of
a page, you may not be able to have all the routines that use certain
identifiers next to each other.
My thought was this...
SCOPE GLOBAL
MyVar1 ds 1
MyVar2 ds 1
MyVar3 ds 1
ENDSCOPE GLOBAL
OVERLAY_START = MyVar3+1
SCOPE OVERLAY1
org OVERLAY_START
MyFoo1 ds 1
MyFoo2 ds 1
ENDSCOPE OVERLAY1
SCOPE OVERLAY2
org OVERLAY_START
MyBar1 ds 1
MyBar2 ds 1
ENDSCOPE OVERLAY2
Then, when you want to work only with variables that are in a certain scope,
surround the section of code like this:
USING OVERLAY1
lda MyFoo1
[...]
sta MyFoo2
ENDUSING OVERLAY1
Anything in the "GLOBAL" scope would be available anywhere, without a USING
declaration. If you reference a variable that isn't allowed (such as
MyBar1), the compiler would report an error.
Maybe "namespace" would be a better name for this than "scope," but I think
this gives the basic idea...
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