From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.5-pre1 (2020-06-20) on ip-172-31-74-118.ec2.internal X-Spam-Level: X-Spam-Status: No, score=-0.9 required=3.0 tests=BAYES_00,FROM_ADDR_WS autolearn=no autolearn_force=no version=3.4.5-pre1 Date: 10 May 93 13:07:50 GMT From: news.intercon.com!psinntp!calspan!westley@louie.udel.edu (Terry J. Westl ey) Subject: Re: Tag values in 9X Message-ID: <1993May10.130750.21680@calspan.com> List-Id: In article <1s8p3h$sud@huon.itd.adelaide.edu.au> andrewd@cs.adelaide.edu.au writes: >The draft LRM for 9X says (14.6.4) "The value used to represent each >tag is determined at the time the corresponding type declaration is >compiled." > >I have a couple of questions about this. > >Scenario 1. Jane creates some tagged types, writes them to a file >using stream io, and sends the file to Fred, with the message "Here >are the sources I used to create the file." Can Fred, using the same >architecture/compiler be guaranteed to read correctly the file he >receives from Jane? That is, will the same tag values be generated at >both ends? I have a question along these lines. We have built a TCP/IP communication system which sends messages between heterogeneous architectures (SPARC and MC68030) using Verdix' compiler. We have adopted a convention whereby we MUST fully specified the message with representation clauses to assure it has the same structure on both architectures. I am evaluating this system for conversion to 9X, primarily because we can use a class of messages rooted at the default message which is a header (source, destination, message id, etc.) only. This avoids the current problem of converting to/from arrays of bytes where multiple message types must be handled, thereby losing type checking. The question is this: How can I specify the tag in the record representation clause? And, as Mr. Dunstan has pointed out, how can I be sure that the tag will identify the same type in both systems? > >andrew > ># Andrew Dunstan # There's nothing good or bad # ># net: # # ># adunstan@steptoe.adl.csa.oz.au # but thinking makes it so. # ># or: andrewd@cs.adelaide.edu.au # # -- Terry J. Westley, Principal Computer Scientist Calspan Corporation, P.O. Box 400, Buffalo, NY 14225 westley@calspan.com Let's hear it for smart mailers that cut off long signa