RE: Ext-desc I/O using data structures (was:Field record relatio

Lorne,

Data structure IO for externally described files comes in handy if you want to 
manipulate an entire record with one operation, as opposed to one operation for 
each field (and what happens when you add more fields?).  You could externally 
describe the data structire and program describe the file, but you lose the 
ability to use keyed IO with key lists, partial keys, etc.  Consider that you 
could:

1) Define an externally described file.
2) Define an externally described data structure using the same file def.
3) Define a stand-alone field "like" the previous data structure.
4) Specify the DS name on an input instruction.
5) Copy the contents of the ext DS to the "like" field with one MOVE.
6) Copy the contents back with one MOVE.

This cannot be done now with externally described files, meaning, for example,  
that I could not use a composite key for the input operation.  This also allows 
me to not have to change the program if fields are added or removed from the 
file--just recompile.  IMHO, this would be a very welcome feature.



On Thu, 2 Apr 1998 10:20:33 -0500, Lorne Sturgeoff wrote:

>I don't see the point of DS I/O for ext-desc files.  You can still have an 
externally described DS for that file.  Normal input operations will move 
database values into the subfields.  DS I/O if very useful for program 
described 
files.
>
>-----Original Message-----
>From:  Hans Boldt [SMTP:boldt@ca.ibm.com]
>Sent:  Thursday, April 02, 1998 8:38 AM
>To:    MIDRANGE-L@midrange.com
>Subject:       Ext-desc I/O using data structures (was:Field record relatio
>
>Hi David!  Yes, you're right.  DS I/O is not allowed for ext-desc files in
>RPG.
>
>Would you (or any other RPG programmer watching) like that limitation
>removed in a future release?  IMHO, ext-desc data structures are very
>useful and we should do more to support them.
>
>Hans Boldt, ILE RPG Development, IBM Toronto Lab, boldt@ca.ibm.com
>




------------------------------
Greg Thielen
Magellan Software, Inc.
Home:   gregt@isda.com
Office: gthielen@magsoft.com
        http://www.magsoft.com


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