Re: John McCarthy died today.

From	Keith Thompson <kst-u@mib.org>
Newsgroups	comp.lang.c
Subject	Re: John McCarthy died today.
Date	2011-11-09 13:25 -0800
Organization	None to speak of
Message-ID	<lnehxhasz6.fsf@nuthaus.mib.org> (permalink)
References	(11 earlier) <8a3ee570-307b-46b4-8e39-996082e716fc@s5g2000vbe.googlegroups.com> <ln7h3acl4i.fsf@nuthaus.mib.org> <j9ca4i$gt7$1@speranza.aioe.org> <lnr51ib0bn.fsf@nuthaus.mib.org> <b90b4feb-800f-41d4-936b-ee5836612d0d@e3g2000vbs.googlegroups.com>

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Malcolm McLean <malcolm.mclean5@btinternet.com> writes:
> On Nov 9, 2:34 am, Keith Thompson <ks...@mib.org> wrote:
>>
>> So tell us, how would you address the problem of existing code that
>> uses "=" for assignment, and of new code using ":=" for assignment
>> that would no longer compile with older compilers?  Similarly,
>> how would you address the legions of C programmers who believe
>> (rightly or wrongly) that using "=" for assignment and "==" for
>> equality is ok, and doesn't need to be fixed?
>>
> You need to make the change compulsory, so the Luddites will have to
> use old compilers. Otherwise you get a worse mess than the one you
> were trying to solve.  The new compiler gives an error, "old style
> assignment operator: please run makenewstyle". So you type
> makenewstyle *.c, and within seconds, all your code compiles.

And you check it all into your source control system, and re-test
everything, and re-release all of it.  Updating the source files
is a tiny fraction of the overhead imposed by a change like this.

> There are some potential problems with diff and so on. If you've got a
> decent version control system then the new code is just flagged as a
> "new version", and it's no different to adding a comment, maybe a
> copyright notice to comply with new corporate policy. But there will
> be people for whom having two logically identical but textually
> different source files will be a nuisance. Then for a while there will
> be both old and new compilers in existence. You can't break old code
> without some problems.
>
> However old code with implict int will generate an unacceptable
> cascade of warnings on new compilers. implicit int has just about died
> out, together with old style function declarations. Changes are
> possible.

The use of implicit int was never mandatory.  The 1989 ANSI standard
kept the feature.  C99 dropped it, but most compilers still accept
it with a warning.  And if you change all your old code to declare
return types explicitly, it still compiles with old compilers.

As for old-style function declarations, they're still in the
language, even though they're clearly inferior to prototypes.
Even in the latest C201X draft they're still merely "an obsolescent
feature"; compilers are still required to support them.

In both cases, the changes to source code could be made
incrementally.

Changing "=" to ":=" as you propose is an all-or-nothing change.
If the C201X standard made such a change (it won't), there would
be a transition period of, probably, a couple of decades in which
you could either ignore the new standard altogether (the most
likely outcome for most programmers), *or* you could maintain two
versions of every single C source file.  That maintenance could be
largely automated, but there would be as many inconsistent automated
solutions as there are development environments.

Oh, and try getting agreement from the C++ standard committee while
you're at it.  And Objective-C (I don't know whether there's a
committee for that, but Objective-C is closely upward-compatible
with C).

If your goal is to kill an future development of the C standard,
making a wide-reaching change like this for fairly trivial benefit
is a good way to do it.

Or here's another idea.  Leave "=" the way it is, and let compilers
issue an optional warning when "=" is used in a context where "=="
is probably what was meant.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

Thread

John McCarthy died today. Kaz Kylheku <kaz@kylheku.com> - 2011-10-25 00:44 +0000
  Re: John McCarthy died today. Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-10-25 01:27 -0700
  Re: John McCarthy died today. Kleuskes & Moos <kleuske@somewhere.else.net> - 2011-10-25 09:27 +0000
  Re: John McCarthy died today. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-10-25 11:27 +0100
  Re: John McCarthy died today. Ark <akhasin@macroexpressions.com> - 2011-10-29 13:33 -0400
    Re: John McCarthy died today. Willem <willem@toad.stack.nl> - 2011-10-29 17:51 +0000
      Re: John McCarthy died today. Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2011-10-29 21:28 +0300
      Re: John McCarthy died today. Keith Thompson <kst-u@mib.org> - 2011-10-29 11:57 -0700
        Re: John McCarthy died today. Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-10-30 08:20 -0700
      Re: John McCarthy died today. Ark <akhasin@macroexpressions.com> - 2011-11-04 05:20 -0400
        Re: John McCarthy died today. Kaz Kylheku <kaz@kylheku.com> - 2011-11-04 15:53 +0000
          Re: John McCarthy died today. James Kuyper <jameskuyper@verizon.net> - 2011-11-04 12:16 -0400
            Re: John McCarthy died today. Kaz Kylheku <kaz@kylheku.com> - 2011-11-04 17:58 +0000
              Re: John McCarthy died today. James Kuyper <jameskuyper@verizon.net> - 2011-11-04 20:49 -0400
                Re: John McCarthy died today. Kaz Kylheku <kaz@kylheku.com> - 2011-11-05 01:55 +0000
                Re: John McCarthy died today. "BartC" <bc@freeuk.com> - 2011-11-07 10:54 +0000
                Re: John McCarthy died today. "Charles Richmond" <netnews@aquaporin4.com> - 2011-11-07 07:36 -0600
                Re: John McCarthy died today. Kaz Kylheku <kaz@kylheku.com> - 2011-11-07 19:49 +0000
                Re: John McCarthy died today. James Kuyper <jameskuyper@verizon.net> - 2011-11-07 15:49 -0500
                Re: John McCarthy died today. Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-11-08 00:38 -0800
                Re: John McCarthy died today. James Kuyper <jameskuyper@verizon.net> - 2011-11-08 07:05 -0500
                Re: John McCarthy died today. lawrence.jones@siemens.com - 2011-11-08 09:12 -0500
                Re: John McCarthy died today. Kaz Kylheku <kaz@kylheku.com> - 2011-11-08 16:48 +0000
                Re: John McCarthy died today. James Kuyper <jameskuyper@verizon.net> - 2011-11-08 12:12 -0500
                Re: John McCarthy died today. Kaz Kylheku <kaz@kylheku.com> - 2011-11-08 23:27 +0000
                Re: John McCarthy died today. Keith Thompson <kst-u@mib.org> - 2011-11-08 14:10 -0800
                Re: John McCarthy died today. James Kuyper <jameskuyper@verizon.net> - 2011-11-08 17:16 -0500
                Re: John McCarthy died today. lawrence.jones@siemens.com - 2011-11-09 13:51 -0500
                Re: Looping Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2011-11-09 19:21 -0700
                Re: Looping Kaz Kylheku <kaz@kylheku.com> - 2011-11-10 02:34 +0000
                Re: John McCarthy died today. Joe Wright <joewwright@comcast.net> - 2011-11-08 17:49 -0500
                Re: John McCarthy died today. Keith Thompson <kst-u@mib.org> - 2011-11-08 16:35 -0800
                Re: John McCarthy died today. Joe Wright <joewwright@comcast.net> - 2011-11-09 01:08 -0500
                Re: John McCarthy died today. Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-11-09 01:26 -0800
                Re: John McCarthy died today. Joe Wright <joewwright@comcast.net> - 2011-11-09 08:18 -0500
                Re: John McCarthy died today. Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-11-09 05:32 -0800
                Re: John McCarthy died today. Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-11-09 01:24 -0800
                Re: John McCarthy died today. Quentin Carbonneaux <qcarbonn@invalid.com> - 2011-11-09 11:59 +0000
                Re: John McCarthy died today. Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-11-09 05:34 -0800
                Re: John McCarthy died today. Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2011-11-08 18:31 +0200
                Re: John McCarthy died today. Keith Thompson <kst-u@mib.org> - 2011-11-07 14:06 -0800
                Re: John McCarthy died today. "BartC" <bc@freeuk.com> - 2011-11-08 02:01 +0000
                Re: John McCarthy died today. Keith Thompson <kst-u@mib.org> - 2011-11-07 23:16 -0800
                Re: John McCarthy died today. Kaz Kylheku <kaz@kylheku.com> - 2011-11-08 05:18 +0000
                Re: John McCarthy died today. Keith Thompson <kst-u@mib.org> - 2011-11-07 23:17 -0800
                Re: John McCarthy died today. Malcolm McLean <malcolm.mclean5@btinternet.com> - 2011-11-08 01:46 -0800
                Re: John McCarthy died today. "BartC" <bc@freeuk.com> - 2011-11-08 13:02 +0000
                Re: John McCarthy died today. Keith Thompson <kst-u@mib.org> - 2011-11-08 14:19 -0800
                Re: John McCarthy died today. Edward Rutherford <edward.p.rutherford79@REMOVETHIS.gmail.com> - 2011-11-08 22:23 +0000
                Re: John McCarthy died today. James Kuyper <jameskuyper@verizon.net> - 2011-11-08 18:13 -0500
                Re: John McCarthy died today. Kaz Kylheku <kaz@kylheku.com> - 2011-11-08 23:38 +0000
                Re: John McCarthy died today. Kaz Kylheku <kaz@kylheku.com> - 2011-11-08 23:18 +0000
                Re: John McCarthy died today. Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2011-11-10 12:40 +0200
                Re: John McCarthy died today. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-11-10 11:39 +0000
                Re: John McCarthy died today. "BartC" <bc@freeuk.com> - 2011-11-10 12:23 +0000
                Re: John McCarthy died today. 88888 Dihedral <dihedral88888@googlemail.com> - 2011-11-10 05:38 -0800
                Re: John McCarthy died today. Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2011-11-10 17:29 +0200
                Re: John McCarthy died today. David Thompson <dave.thompson2@verizon.net> - 2011-11-21 02:39 -0500
                Re: John McCarthy died today. Keith Thompson <kst-u@mib.org> - 2011-11-08 16:34 -0800
                Re: John McCarthy died today. Malcolm McLean <malcolm.mclean5@btinternet.com> - 2011-11-09 01:37 -0800
                Re: John McCarthy died today. Keith Thompson <kst-u@mib.org> - 2011-11-09 13:25 -0800
                Re: John McCarthy died today. Ian Collins <ian-news@hotmail.com> - 2011-11-10 10:36 +1300
                Re: John McCarthy died today. Malcolm McLean <malcolm.mclean5@btinternet.com> - 2011-11-09 23:47 -0800
                Re: John McCarthy died today. Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-11-10 00:21 -0800
                Re: John McCarthy died today. Keith Thompson <kst-u@mib.org> - 2011-11-10 03:04 -0800
                Re: John McCarthy died today. gazelle@shell.xmission.com (Kenny McCormack) - 2011-11-10 15:20 +0000
                Re: John McCarthy died today. Jorgen Grahn <grahn+nntp@snipabacken.se> - 2011-11-12 23:22 +0000
                Re: John McCarthy died today. Kaz Kylheku <kaz@kylheku.com> - 2011-11-13 01:44 +0000
                Re: John McCarthy died today. "Charles Richmond" <netnews@aquaporin4.com> - 2011-11-13 04:18 -0600
                Re: John McCarthy died today. Kaz Kylheku <kaz@kylheku.com> - 2011-11-13 16:57 +0000
                Re: John McCarthy died today. Robert Wessel <robertwessel2@yahoo.com> - 2011-11-13 11:59 -0600
                Re: John McCarthy died today. gazelle@shell.xmission.com (Kenny McCormack) - 2011-11-13 18:54 +0000
                Re: John McCarthy died today. Keith Thompson <kst-u@mib.org> - 2011-11-13 14:47 -0800
                Re: John McCarthy died today. Kaz Kylheku <kaz@kylheku.com> - 2011-11-14 03:43 +0000
                Re: John McCarthy died today. Ike Naar <ike@sverige.freeshell.org> - 2011-11-14 09:00 +0000
                Re: John McCarthy died today. Kaz Kylheku <kaz@kylheku.com> - 2011-11-14 18:30 +0000
                Re: John McCarthy died today. James Kuyper <jameskuyper@verizon.net> - 2011-11-14 14:44 -0500
                Re: John McCarthy died today. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-11-14 20:13 +0000
                Re: John McCarthy died today. Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-11-14 00:21 -0800
                Re: John McCarthy died today. Lauri Alanko <la@iki.fi> - 2011-11-10 15:26 +0000
                Re: John McCarthy died today. Kaz Kylheku <kaz@kylheku.com> - 2011-11-10 01:51 +0000
                Re: John McCarthy died today. Edward Rutherford <edward.p.rutherford79@REMOVETHIS.gmail.com> - 2011-11-09 17:15 +0000
                Re: John McCarthy died today. "BartC" <bc@freeuk.com> - 2011-11-09 18:04 +0000
                Re: John McCarthy died today. Keith Thompson <kst-u@mib.org> - 2011-11-09 13:31 -0800
                Re: John McCarthy died today. Robert Wessel <robertwessel2@yahoo.com> - 2011-11-09 15:53 -0600
                Re: John McCarthy died today. "BartC" <bc@freeuk.com> - 2011-11-09 22:02 +0000
                Re: John McCarthy died today. Keith Thompson <kst-u@mib.org> - 2011-11-09 14:14 -0800
                Re: John McCarthy died today. Keith Thompson <kst-u@mib.org> - 2011-11-09 13:50 -0800
                Re: John McCarthy died today. James Kuyper <jameskuyper@verizon.net> - 2011-11-08 07:10 -0500
          Re: John McCarthy died today. Keith Thompson <kst-u@mib.org> - 2011-11-04 14:51 -0700

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