Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!uakari.primate.wisc.edu!aplcen!aplcomm!uunet!weyrich!orville
From: orville@weyrich.UUCP (Orville R. Weyrich)
Newsgroups: comp.lang.fortran
Subject: Re: Order of variables in EQUIVALENCE statement
Message-ID: <1991Jun19.092500.2008@weyrich.UUCP>
Date: 19 Jun 91 09:25:00 GMT
References: <99850@lll-winken.LLNL.GOV> <1991Jun18.195315.18248@wdl1.wdl.loral.com>
Reply-To: orville@weyrich.UUCP (Orville R. Weyrich)
Distribution: na
Organization: Weyrich Computer Consulting
Lines: 27

In article <1991Jun18.195315.18248@wdl1.wdl.loral.com> ekman@wdl30.wdl.loral.com (Donald Ekman) writes:
>In article <99850@lll-winken.LLNL.GOV> lindner@ncis.llnl.gov (Curt Lindner) writes:
>>I've been in the the process of converting some code using 'f77cvt' on 
>>a SUN Sparcstation. 
>>
>>The conversion is swapping the variables in the equivalence statements,
>>which it shouldn't do, as far as I can tell. 
>>
>>Does this have an adverse affect on the results of the code, i.e. does the
>>first variable take on the value of the second, or vice versa??
>>
>Since the equivalence statement simply causes each of the variable names to
>reference the same storage location, the order is irrelevant, I believe.

I would agree with you from the point of view of program correctness. 
However ...
I don't know about Sparcstations, but word-boundary alignment problems
used to haunt old IBM mainframes, and so the order could affect run-time
efficiency if the equivalenced variables were of different data types.


--------------------------------------           ******************************
Orville R. Weyrich, Jr., Ph.D.                   Certified Systems Professional
Internet: orville%weyrich@uunet.uu.net             Weyrich Computer Consulting
Voice:    (602) 391-0821                         POB 5782, Scottsdale, AZ 85261
Fax:      (602) 391-0023                              (Yes! I'm available)
--------------------------------------           ******************************