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Re: Casts on lvalues

From glen herrmannsfeldt <gah@ugcs.caltech.edu>
Newsgroups comp.lang.c
Subject Re: Casts on lvalues
Date 2012-12-07 22:18 +0000
Organization Aioe.org NNTP Server
Message-ID <k9tput$9kv$1@speranza.aioe.org> (permalink)
References (8 earlier) <k9sqi4$do2$1@dont-email.me> <ftmws.280907$kt5.95535@fx08.am4> <50C216B3.60103@verizon.net> <k9t999$r5g$1@speranza.aioe.org> <4zqws.788610$vW7.211303@fx19.am4>

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BartC <bc@freeuk.com> wrote:
> "glen herrmannsfeldt" <gah@ugcs.caltech.edu> wrote in message 
> news:k9t999$r5g$1@speranza.aioe.org...
>> James Kuyper <jameskuyper@verizon.net> wrote:

(snip on EQUIVALENCE)

>>> Its been a couple of decades since the last time I wrote much Fortran
>>> code, and I don't think I ever used that feature, but I was aware of it.
>>> If it has the same capability you describe above, I didn't remember 
>>> that fact, which isn't particularly surprising.

>> Fortran EQUIVALENCE has many of the same restrictions as union, though
>> it is often used to get bits between different types.
 
> This page shows you can still set up all sorts of relationships between 
> unrelated data:
 
> http://docs.oracle.com/cd/E19957-01/805-4939/6j4m0vn9b/index.html

EQUIVALENCE goes back to the first Fortran compiler, usually called 
Fortran I, in 1956. It required at least 4K (36 bit) words to run.
A 704 with the full 32K (36 bit) words was pretty much the super
computer of the time. EQUIVALENCE was needed to conserve memory
use, and much less for type punning. 

But yes, in later years, with more memory available, EQUIVALENCE
was commonly used to move bits between different data types.

TRANSFER wasn't added until, I believe, Fortran 90.
(Fortran 90 added dynamic allocation, which doesn't work
with EQUIVALENCE.)

-- glen

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Thread

Casts on lvalues "BartC" <bc@freeuk.com> - 2012-12-02 13:23 +0000
  Re: Casts on lvalues SG <sgesemann@gmail.invalid> - 2012-12-02 14:40 +0100
  Re: Casts on lvalues Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-12-02 13:53 +0000
    Re: Casts on lvalues "BartC" <bc@freeuk.com> - 2012-12-06 12:26 +0000
      Re: Casts on lvalues Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-12-06 15:15 +0000
      Re: Casts on lvalues Keith Thompson <kst-u@mib.org> - 2012-12-06 12:05 -0800
  Re: Casts on lvalues Keith Thompson <kst-u@mib.org> - 2012-12-02 12:34 -0800
    Re: Casts on lvalues "BartC" <bc@freeuk.com> - 2012-12-02 21:18 +0000
      Re: Casts on lvalues Willem <willem@turtle.stack.nl> - 2012-12-05 22:36 +0000
        Re: Casts on lvalues "BartC" <bc@freeuk.com> - 2012-12-05 23:46 +0000
          Re: Casts on lvalues Willem <willem@turtle.stack.nl> - 2012-12-06 18:35 +0000
    Re: Casts on lvalues pete <pfiland@mindspring.com> - 2012-12-02 16:21 -0500
      Re: Casts on lvalues Eric Sosman <esosman@comcast-dot-net.invalid> - 2012-12-02 17:10 -0500
        Re: Casts on lvalues pete <pfiland@mindspring.com> - 2012-12-02 18:50 -0500
      Re: Casts on lvalues James Kuyper <jameskuyper@verizon.net> - 2012-12-02 19:14 -0500
  Re: Casts on lvalues falk@rahul.net (Edward A. Falk) - 2012-12-04 23:57 +0000
    Re: Casts on lvalues "BartC" <bc@freeuk.com> - 2012-12-05 01:35 +0000
      Re: Casts on lvalues Piotr Kalinowski <pitkali@gmail.com> - 2012-12-05 16:07 +0100
        Re: Casts on lvalues "BartC" <bc@freeuk.com> - 2012-12-05 16:47 +0000
          Re: Casts on lvalues Eric Sosman <esosman@comcast-dot-net.invalid> - 2012-12-05 13:04 -0500
            Re: Casts on lvalues "BartC" <bc@freeuk.com> - 2012-12-05 18:39 +0000
              Re: Casts on lvalues James Kuyper <jameskuyper@verizon.net> - 2012-12-05 14:23 -0500
                Re: Casts on lvalues "BartC" <bc@freeuk.com> - 2012-12-05 22:11 +0000
                Re: Casts on lvalues Ian Collins <ian-news@hotmail.com> - 2012-12-06 11:51 +1300
                Re: Casts on lvalues "BartC" <bc@freeuk.com> - 2012-12-05 23:58 +0000
                Re: Casts on lvalues Piotr Kalinowski <pitkali@gmail.com> - 2012-12-06 22:00 +0100
                Re: Casts on lvalues glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-06 03:05 +0000
              Re: Casts on lvalues Eric Sosman <esosman@comcast-dot-net.invalid> - 2012-12-05 14:43 -0500
              Re: Casts on lvalues Greg Martin <greg@softsprocket.com> - 2012-12-05 12:25 -0800
                Re: Casts on lvalues "BartC" <bc@freeuk.com> - 2012-12-05 21:57 +0000
                Re: Casts on lvalues Keith Thompson <kst-u@mib.org> - 2012-12-05 16:09 -0800
                Re: Casts on lvalues Philipp Thomas <kthomas@linux01.gwdg.de> - 2012-12-07 01:24 +0100
                Re: Casts on lvalues Keith Thompson <kst-u@mib.org> - 2012-12-06 17:22 -0800
                Re: Casts on lvalues Öö Tiib <ootiib@hot.ee> - 2012-12-07 00:31 -0800
                Re: Casts on lvalues James Kuyper <jameskuyper@verizon.net> - 2012-12-07 08:18 -0500
                Re: Casts on lvalues Öö Tiib <ootiib@hot.ee> - 2012-12-07 09:07 -0800
                Re: Casts on lvalues Keith Thompson <kst-u@mib.org> - 2012-12-07 11:01 -0800
                Re: Casts on lvalues glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-07 21:57 +0000
                Re: Casts on lvalues Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-12-07 22:29 +0000
                Re: Casts on lvalues glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-08 00:04 +0000
                Re: Casts on lvalues lawrence.jones@siemens.com - 2012-12-15 16:51 -0500
                Re: Casts on lvalues Keith Thompson <kst-u@mib.org> - 2012-12-15 15:48 -0800
                Re: Casts on lvalues lawrence.jones@siemens.com - 2012-12-17 16:37 -0500
                Re: Casts on lvalues Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-17 02:58 -0800
                Re: Casts on lvalues Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-17 02:53 -0800
                Re: Casts on lvalues Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-17 02:43 -0800
              Re: Casts on lvalues Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-12-05 22:07 +0000
                Re: Casts on lvalues "BartC" <bc@freeuk.com> - 2012-12-05 22:20 +0000
                Re: Casts on lvalues Keith Thompson <kst-u@mib.org> - 2012-12-05 16:10 -0800
                Re: Casts on lvalues Philip Lantz <prl@canterey.us> - 2012-12-06 22:49 -0800
                Re: Casts on lvalues "BartC" <bc@freeuk.com> - 2012-12-07 12:54 +0000
                Re: Casts on lvalues James Kuyper <jameskuyper@verizon.net> - 2012-12-07 08:22 -0500
                Re: Casts on lvalues "BartC" <bc@freeuk.com> - 2012-12-07 13:48 +0000
                Re: Casts on lvalues James Kuyper <jameskuyper@verizon.net> - 2012-12-07 11:17 -0500
                Re: Casts on lvalues glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-07 17:33 +0000
                Re: Casts on lvalues "BartC" <bc@freeuk.com> - 2012-12-07 18:28 +0000
                Re: Casts on lvalues glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-07 22:18 +0000
                Re: Casts on lvalues "BartC" <bc@freeuk.com> - 2012-12-07 18:27 +0000
                Re: Casts on lvalues James Kuyper <jameskuyper@verizon.net> - 2012-12-07 14:14 -0500
                Re: Casts on lvalues "BartC" <bc@freeuk.com> - 2012-12-07 20:16 +0000
                Re: Casts on lvalues James Kuyper <jameskuyper@verizon.net> - 2012-12-07 15:41 -0500
                Re: Casts on lvalues Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-17 03:03 -0800
              Re: Casts on lvalues Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-12-09 17:54 +0200
                Re: Casts on lvalues James Kuyper <jameskuyper@verizon.net> - 2012-12-09 12:38 -0500
                Re: Casts on lvalues "BartC" <bc@freeuk.com> - 2012-12-09 18:50 +0000
                Re: Casts on lvalues James Kuyper <jameskuyper@verizon.net> - 2012-12-09 14:31 -0500
                Re: Casts on lvalues Keith Thompson <kst-u@mib.org> - 2012-12-09 20:12 -0800
                Re: Casts on lvalues Heikki Kallasjoki <fis+usenet@zem.fi> - 2012-12-10 07:38 +0000
                Re: Casts on lvalues James Kuyper <jameskuyper@verizon.net> - 2012-12-10 08:12 -0500
                Re: Casts on lvalues Heikki Kallasjoki <fis+usenet@zem.fi> - 2012-12-10 17:46 +0000
                Re: Casts on lvalues James Kuyper <jameskuyper@verizon.net> - 2012-12-10 12:59 -0500
                Re: Casts on lvalues Keith Thompson <kst-u@mib.org> - 2012-12-10 12:07 -0800
                Re: Casts on lvalues Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-17 03:11 -0800
                Re: Casts on lvalues Ian Collins <ian-news@hotmail.com> - 2012-12-10 20:50 +1300
                Re: Casts on lvalues James Kuyper <jameskuyper@verizon.net> - 2012-12-10 07:49 -0500
  Re: Casts on lvalues Rui Maciel <rui.maciel@gmail.com> - 2012-12-07 15:19 +0000
    Re: Casts on lvalues "BartC" <bc@freeuk.com> - 2012-12-07 16:54 +0000

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