Re: overlaying arrays in v5r1

No disagreement, just one additional comment re the based technique.

I've seen way too many people make the assumption that if fields are contiguous in a record then using the pointer technique using the address of the first field to base the array will work.

Really bad idea - very error prone. The only way to guarantee that they are contiguous is to use an externally described or LikeDS structure and read the data into that.


On 2014-01-21, at 11:00 AM, Joe Pluta <lists@xxxxxxxxxxxxxxxxx> wrote:

On 1/21/2014 9:29 AM, Ken Sims wrote:

Oops, my bad! I forgot to mention that when I use this technique, I do
always use a data structure for the record format to ensure that
fields are together in storage as expected. Jon is completely correct
that if you don't use a data structure, there is no guarantee the
fields will be contiguous in storage.

Yes, this is the primary point. If the fields are already in a data
structure (e.g., an E/DS) and you are absolutely sure that the fields
won't move, then creating a based array pointing to the first field is
the way to go.

Otherwise, create your own data structure with the fields and then you
can use either technique, the based array or the OVERLAY array in the
data structure.

Joe