Re: %lookup on a Data Structure Array

[John Yeung <gallium.arsenide@xxxxxxxxx>]

On Fri, Nov 11, 2011 at 9:52 AM, Kurt Anderson
<kurt.anderson@xxxxxxxxxxxxxx> wrote:
> John,
>
> I don't like storing all the contents of a file in an array
> when I only need certain fields - to reduce questions
> like "why is this field loaded if it's not used?" - which
> is a question I would ask.

You can specify the length in the F-specs, so you don't load the whole
record.  As far as I know, you do have to load contiguous bytes from
the leftmost part of the record, though.  (No one said table files are
elegant or sophisticated.)

> In service programs I'm not a fan of the pre-runtime array.
>  This is a style thing, but in our shop [...]

You could have given this as an explanation for avoiding table files.

>  I really only wanted to whine about the lack of
> complete functionality of data structure arrays.  That
> is to say, I'm a huge fan and use data structure arrays
> a lot now, but it's a bummer that I can't use the binary
> search functionality of %lookup with them.

I agree with the first batch of responses suggesting you use subfields
and overlays.  (That was my first thought when I read your original
question, and I knew that plenty of other people would give you that
answer.)  It's the closest thing to what you want; it's what people
did before data structure arrays (lots of folks still don't have data
structure arrays, like me); and in my opinion it strikes a good
balance between performance, resource usage, ease of implementation,
and ease of maintenance.

John