Re: Array overlay

[Barbara Morris <bmorris@xxxxxxxxxx>]

CWilt@xxxxxxxxxxxx wrote:
> 
> Barbara (or anyone else)
> 
> Can you provide some more detail on what is going on here.  Specifically,
> what's the relationship/use of MaxPtyAlpha and MaxPtyA?
> 
> > And to eliminate the hardcoding of the dimension:
> >
> >      D  MaxPtyAlpha
> >      D   MaxPtyA                           Overlay(MaxPtyAlpha)
> >      D    MaxPty1                    10i 0 Overlay(MaxPtyA:*next)
> > ...
> >      D    MaxPty                     10i 0 Overlay(MaxPtyAlpha)
> >      D                                     Dim(%Div(%Size(MaxPtyA)
> >      D                                             :%Size(MaxPty1)))
> >

If I tried to define MaxPty with Overlay(MaxPtyA), then MaxPtyA would
never get defined.  When you have a field like MaxPtyA whose length is
defined by the overlaying fields, then you can't make the definition of
one of the overlaying fields dependent on the definition of the overlaid
field.

Ok, that's pretty well unintelligible ... let me try again.

If I code the following, then the length of Over is determined by the
lengths of Elem1 and ElemArr (the fields which overlay it).  The length
of ElemArr depends on its Dim keyword which can't be determined until
Over is defined, because of %Size(Over).  So the definition of Over
depends on the definition of ElemArr which depends on Over ...

      D   Over                           
      D    Elem1                      10i 0 Overlay(Over:*next)
      D    ElemArr                    10i 0 Overlay(Over)
      D                                     Dim(%Div(%Size(Over)
      D                                             :%Size(Elem1)))

So I add an extra field for ElemArr to overlay, so that ElemArr doesn't
have to overlay Over, so Over's size can be determined just by Elem1
etc.

      D  OverOver
      D   Over                              Overlay(OverOver)
      D    Elem1                      10i 0 Overlay(Over:*next)
      D    ElemArr                    10i 0 Overlay(Over)
      D                                     Dim(%Div(%Size(OverOver)
      D                                             :%Size(Elem1)))

Hope that makes sense.