Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.c > #140233

Re: Compiler tests

From Ben Bacarisse <ben.usenet@bsb.me.uk>
Newsgroups comp.lang.c
Subject Re: Compiler tests
Date 2019-01-25 12:04 +0000
Organization A noiseless patient Spider
Message-ID <87va2dvt86.fsf@bsb.me.uk> (permalink)
References (16 earlier) <q2alb9$sg7$1@dont-email.me> <87imyfxcnu.fsf@bsb.me.uk> <q2c4p0$6i3$1@dont-email.me> <871s51y7aq.fsf@bsb.me.uk> <q2enc0$256$1@dont-email.me>

Show all headers | View raw

David Brown <david.brown@hesbynett.no> writes:

> On 25/01/2019 00:17, Ben Bacarisse wrote:
>> David Brown <david.brown@hesbynett.no> writes:
>> 
>>> On 23/01/2019 22:54, Ben Bacarisse wrote:
>> <snip>
>>>> In Algol 68 (one of the first languages to get this right)
>>>>
>>>>   INT x = f(y);
>>>>
>>>> calls f at run-time (optimisations aside) and names the resulting value
>>>> x.  You can't take the address of x because it's has no storage (again
>>>> "as if rules" aside), and you can't alter x because it is not a
>>>> variable.
>>>
>>> I don't see how that differs from C++ :
>>>
>>> 	const int x = f(y);
>>>
>>> You /can/ take the address of x, but that doesn't matter.
>> 
>> Hmm...  why does it not matter?  The point is that the C++ statement
>> says something different to the Algol 68 statement.  In the C++ case, x
>> must have an observable representation because x denotes an object not a
>> value.  It's just nice to be able to write what one means without being
>> obliged to say more.
>
> In what circumstances would you have a named constant value that does
> not have a representation?  Does an Algol "INT" represent an abstract
> integer type, perhaps with unlimited size, rather than a concrete type?
>  (That would be interesting.)

Generalising rather too much, a type, concrete or not, will usually
specify a set of values.  There is no need for a representation, in the
way the term is used in C, even when the range of values is limited.

I am not sure what you mean with the concrete/abstract distinction here.
The range of INT values in Algol 68 will usually be chosen so that they
can be efficiently represented on the hardware that is being targeted.

> I agree that it is nice to be able to write what you mean - no more and
> no less.  But it is rarely possible in programming to get exactly
> that.

Sure.  Never exactly that.  But C is particularly limited in this
regard.  (That's not surprising and I am not "having a go" at C.)

C is an old, low-level language, designed for a very specific purpose.
We know that DMR was much influenced by Algol 68, but I am sure he was
as influenced by the fact that Algol 68 was proving to a challenge to
implement, even on the big machines of the day, as he was by any of the
language features.

> Sometimes it is good to have restrictions on how we can use things
> (objects, functions, whatever) in code.  Declaring objects "const" can
> make it easier to be sure code is correct, help detect mistakes, and
> possibly improve optimisation.  So adding an explicit restriction helps.
>
> But I simply don't see any major benefit in a "no address"
> restriction.

It is clear that most people get by perfectly well using C, regardless
of the restrictions it imposes.  I do too.  So I suppose they can't be
major restrictions.  But naming values (rather than objects) seems like
a very natural thing to me that I can't do in C.

>  I see plenty of efficiency benefit in the compiler being able to avoid
> making an object in memory if it does not need to - but that is an
> implementation issue.  How often have you seen the storage class
> "register" used in C (or C++) programming as a way of saying "don't
> allow the address of this to be taken", rather than as an optimiser hint
> for old compilers?  I would estimate that if you surveyed all the
> regulars in this group and added them together, you still would not need
> two hands to count the cases.  It just isn't something people find
> relevant, AFAICS.

Not being able to take the address is not the issue.  The issue is
naming a value.  Since you can't do that (in any general way) in C I
would not expect the readers of c.l.c to be too worried by it (I'm not),
but how many would say that they write C code with the intent of naming
a value using various means to get round the restriction:

  enum { max_types = 1024 };

  #define begin_token "begin"

  const double pi = 3.1415;

?  I would guess most.

<snip>
-- 
Ben.

Back to comp.lang.c | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Compiler tests Bart <bc@freeuk.com> - 2019-01-20 00:03 +0000
  Re: Compiler tests Ian Collins <ian-news@hotmail.com> - 2019-01-20 16:52 +1300
    Re: Compiler tests "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-20 10:27 +0100
      Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-20 12:37 +0100
        Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-20 13:08 +0000
          Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-20 15:02 +0000
            Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-20 17:31 +0100
              Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-20 17:08 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-20 21:40 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-20 22:41 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-21 00:39 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-21 00:36 +0000
                Re: Compiler tests Ian Collins <ian-news@hotmail.com> - 2019-01-21 16:33 +1300
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-21 11:58 +0000
                Re: Compiler tests Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2019-01-21 04:15 -0800
                Re: Compiler tests Ian Collins <ian-news@hotmail.com> - 2019-01-22 07:53 +1300
                Re: Compiler tests BGB <cr88192@hotmail.com> - 2019-01-23 01:15 -0600
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-23 12:00 +0000
                Re: Compiler tests Ian Collins <ian-news@hotmail.com> - 2019-01-24 08:13 +1300
                Re: Compiler tests BGB <cr88192@hotmail.com> - 2019-01-23 13:30 -0600
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-21 08:22 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-21 12:23 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-21 14:42 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-21 14:17 +0000
                Re: Compiler tests Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2019-01-21 12:46 -0800
                You guys really, really need to get a room (Was: Compiler tests) gazelle@shell.xmission.com (Kenny McCormack) - 2019-01-24 14:05 +0000
          Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-20 17:27 +0100
            Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-20 17:19 +0000
              Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-21 09:44 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-21 12:49 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-21 15:31 +0100
                Re: Compiler tests jacobnavia <jacob@jacob.remcomp.fr> - 2019-01-21 14:38 +0100
                Re: Compiler tests "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-21 15:15 +0100
                Re: Compiler tests jacobnavia <jacob@jacob.remcomp.fr> - 2019-01-21 16:05 +0100
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-21 16:39 +0100
                Re: Compiler tests Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2019-01-21 12:51 -0800
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-22 00:16 +0000
                Re: Compiler tests jacobnavia <jacob@jacob.remcomp.fr> - 2019-01-22 08:43 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-22 12:31 +0000
                Re: Compiler tests jacobnavia <jacob@jacob.remcomp.fr> - 2019-01-22 17:49 +0100
                Re: Compiler tests jacobnavia <jacob@jacob.remcomp.fr> - 2019-01-23 11:04 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-23 11:18 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-21 15:35 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-21 15:49 +0000
                Re: Compiler tests "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-21 17:42 +0100
                Re: Compiler tests BGB <cr88192@hotmail.com> - 2019-01-23 03:18 -0600
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-23 11:11 +0100
                Re: Compiler tests BGB <cr88192@hotmail.com> - 2019-01-23 12:18 -0600
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-23 13:56 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-22 10:55 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-22 12:07 +0000
                Re: Compiler tests fir <profesor.fir@gmail.com> - 2019-01-22 04:29 -0800
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-22 12:52 +0000
                Re: Compiler tests mark.bluemel@gmail.com - 2019-01-22 05:04 -0800
                Re: Compiler tests fir <profesor.fir@gmail.com> - 2019-01-22 05:18 -0800
                Re: Compiler tests fir <profesor.fir@gmail.com> - 2019-01-22 05:45 -0800
                Re: Compiler tests fir <profesor.fir@gmail.com> - 2019-01-22 05:35 -0800
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-22 15:10 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-22 17:30 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-22 23:02 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-22 23:14 +0000
                Re: Compiler tests Keith Thompson <kst-u@mib.org> - 2019-01-22 15:45 -0800
                Re: Compiler tests Robert Wessel <robertwessel2@yahoo.com> - 2019-01-22 17:57 -0600
                Re: Compiler tests Keith Thompson <kst-u@mib.org> - 2019-01-22 16:36 -0800
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-23 01:37 +0000
                Re: Compiler tests Keith Thompson <kst-u@mib.org> - 2019-01-22 18:53 -0800
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-23 09:42 +0100
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-23 09:22 +0100
                Re: Compiler tests James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-01-23 08:52 -0500
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-23 15:13 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-23 14:33 +0000
                Re: Compiler tests James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-01-23 07:30 -0800
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-23 16:05 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-23 17:17 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-23 16:29 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-23 22:04 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-23 21:50 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-24 10:45 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-24 11:55 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-24 13:58 +0100
                Re: Compiler tests mark.bluemel@gmail.com - 2019-01-24 05:07 -0800
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-24 14:10 +0000
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-24 14:18 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-24 15:51 +0100
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-24 15:44 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-24 17:32 +0000
                Re: Compiler tests scott@slp53.sl.home (Scott Lurndal) - 2019-01-24 19:07 +0000
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-24 20:14 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-24 22:24 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-24 22:46 +0000
                Re: Compiler tests Ian Collins <ian-news@hotmail.com> - 2019-01-25 12:34 +1300
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-25 01:01 +0000
                Re: Compiler tests Ian Collins <ian-news@hotmail.com> - 2019-01-25 14:15 +1300
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-25 10:05 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-25 14:51 +0000
                Re: Compiler tests Mateusz Viste <mateusz@wont.tell> - 2019-01-25 09:48 +0000
                Re: Compiler tests "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-25 10:56 +0100
                Re: Compiler tests Mateusz Viste <mateusz@wont.tell> - 2019-01-25 12:08 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-25 13:28 +0100
                Re: Compiler tests Mateusz Viste <mateusz@wont.tell> - 2019-01-25 13:33 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-25 15:38 +0100
                Re: Compiler tests Mateusz Viste <mateusz@wont.tell> - 2019-01-25 15:08 +0000
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-25 13:53 +0000
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-25 12:25 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-25 10:03 +0100
                Re: Compiler tests "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-25 10:08 +0100
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-25 11:14 +0100
                Re: Compiler tests "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-25 12:02 +0100
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-25 13:37 +0100
                Re: Compiler tests "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-25 13:58 +0100
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-25 14:26 +0100
                Re: Compiler tests "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-25 15:01 +0100
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-25 15:42 +0100
                Re: Compiler tests Keith Thompson <kst-u@mib.org> - 2019-01-25 10:25 -0800
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-25 14:37 +0000
                Re: Compiler tests "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-25 16:33 +0100
                Re: Compiler tests Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2019-01-25 07:44 -0800
                Re: Compiler tests "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-25 17:53 +0100
                Re: Compiler tests Keith Thompson <kst-u@mib.org> - 2019-01-25 10:33 -0800
                Re: Compiler tests "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-25 20:43 +0100
                Re: Compiler tests Keith Thompson <kst-u@mib.org> - 2019-01-25 12:17 -0800
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-25 18:31 +0000
                Re: Compiler tests "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-25 20:41 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-25 21:19 +0000
                Re: Compiler tests Ian Collins <ian-news@hotmail.com> - 2019-01-26 10:24 +1300
                Re: Compiler tests "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-25 22:27 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-25 22:39 +0000
                Re: Compiler tests Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-01-25 18:46 +0000
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-25 12:43 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-25 14:37 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-25 14:19 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-25 15:47 +0100
                Re: Compiler tests Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2019-01-25 07:17 -0800
                Re: Compiler tests Jorgen Grahn <grahn+nntp@snipabacken.se> - 2019-02-03 07:28 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-02-03 12:35 +0100
                Re: Compiler tests Jorgen Grahn <grahn+nntp@snipabacken.se> - 2019-02-03 21:47 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-02-03 22:57 +0100
                Re: Compiler tests Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2019-01-24 06:47 -0800
                Re: Compiler tests Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-01-23 20:22 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-23 22:12 +0100
                Re: Compiler tests Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-01-23 21:54 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-24 11:41 +0100
                Re: Compiler tests Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-01-24 23:17 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-25 11:11 +0100
                Re: Compiler tests Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-01-25 12:04 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-25 14:05 +0100
                Re: Compiler tests Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-01-25 18:40 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-25 22:36 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-25 22:15 +0000
                Re: Compiler tests scott@slp53.sl.home (Scott Lurndal) - 2019-01-25 14:48 +0000
                Re: Compiler tests scott@slp53.sl.home (Scott Lurndal) - 2019-01-25 14:46 +0000
                Re: Compiler tests Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-01-25 17:48 +0000
                Re: Compiler tests James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-01-23 08:23 -0800
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-23 16:41 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-23 16:18 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-23 17:28 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-23 20:23 +0000
                Re: Compiler tests Robert Wessel <robertwessel2@yahoo.com> - 2019-01-22 17:52 -0600
          Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-20 20:17 +0000
    Re: Compiler tests BGB <cr88192@hotmail.com> - 2019-01-21 00:13 -0600

csiph-web