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Re: return -1 using size_t???

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Devil with the China Blue Dress <chine.bleu@yahoo.com> writes:
> In article <4F36F7C4.5060103@loria.fr>, Jens Gustedt <jens.gustedt@loria.fr> 
> wrote:
[...]
>> For all conforming C implementations the result of converting -1 to
>> size_t is SIZE_MAX.
>
> In 4-bit ones complement, -1 is 1110, but the maximum natural number
> is 1111; signed magnitude are 1001 and 1111; twos complement are 1111
> and 1111.

Yes, in 4-bit ones'-complement -1 is represented by the bit pattern 1110,
but 1111 would be the representation for negative zero.

> Which came first? Twos complement DEC, Honeywell, and IBM machines or
> the C standard which emulated C implementations on twos complement
> CPUs?  Or did the committee just magically pluck that requirement out
> of the air?

Clearly those machines that use[d] a two's-complement
representation for signed types predate the C standard.  C's rules
for signed-to-unsigned conversion are easiest to implement on a
system that uses two's-complement, and require some extra work on
ones'-complement and sign-and-magnitude systems (which are rare
these days).

It seems clear that two's-complement semantics inspired standard C
semantics.  Nevertheless, C's conversion semantics are now *defined*
without reference to the underlying representation.

Which raises a perhaps interesting question.  Are there any current C
implementations for ones'-complement or sign-and-magnitude systems?
If so, what standard, if any, do they conform to, and how much
extra work do the compilers actually do to conform to the required
semantics for signed-to-unsigned conversion?  For that matter,
are there non-conforming C implementations for such systems that
implement such conversions just by reinterpreting the bits?

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

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return -1 using size_t??? Robert Hayes <rhyes80@gmail.com> - 2012-02-11 11:21 -0800
  Re: return -1 using size_t??? Shao Miller <sha0.miller@gmail.com> - 2012-02-11 15:00 -0500
    Re: return -1 using size_t??? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-11 23:24 +0000
  Re: return -1 using size_t??? Jeffrey R <joeff@nospam.com> - 2012-02-11 19:58 +0000
    Re: return -1 using size_t??? Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-02-11 15:11 -0500
  Re: return -1 using size_t??? Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-02-11 15:07 -0500
    Re: return -1 using size_t??? Robert Hayes <rhyes80@gmail.com> - 2012-02-11 12:42 -0800
      Re: return -1 using size_t??? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-02-11 13:19 -0800
        Re: return -1 using size_t??? Keith Thompson <kst-u@mib.org> - 2012-02-11 17:10 -0800
          Re: return -1 using size_t??? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-02-12 03:48 -0800
            Re: return -1 using size_t??? Keith Thompson <kst-u@mib.org> - 2012-02-12 04:04 -0800
      Re: return -1 using size_t??? Jeffrey R <joeff@nospam.com> - 2012-02-11 22:25 +0000
        Re: return -1 using size_t??? Devil with the China Blue Dress <chine.bleu@yahoo.com> - 2012-02-11 14:36 -0800
          Re: return -1 using size_t??? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-11 23:17 +0000
        Re: return -1 using size_t??? Jeroen Mostert <jmostert@xs4all.nl> - 2012-02-11 23:46 +0100
          Re: return -1 using size_t??? pete <pfiland@mindspring.com> - 2012-02-11 19:18 -0500
        Re: return -1 using size_t??? Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-02-12 08:38 -0500
      Re: return -1 using size_t??? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-11 23:32 +0000
      Re: return -1 using size_t??? pete <pfiland@mindspring.com> - 2012-02-11 19:15 -0500
    Re: return -1 using size_t??? Ralph Spitzner <rasp@spitzner.org> - 2012-02-13 13:51 +0100
  Re: return -1 using size_t??? Devil with the China Blue Dress <chine.bleu@yahoo.com> - 2012-02-11 12:40 -0800
    Re: return -1 using size_t??? Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-02-11 17:02 -0500
      Re: return -1 using size_t??? Devil with the China Blue Dress <chine.bleu@yahoo.com> - 2012-02-11 14:11 -0800
        Re: return -1 using size_t??? Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-02-11 17:21 -0500
          Re: return -1 using size_t??? Devil with the China Blue Dress <chine.bleu@yahoo.com> - 2012-02-11 14:31 -0800
            Re: return -1 using size_t??? Willem <willem@toad.stack.nl> - 2012-02-11 22:52 +0000
            Re: return -1 using size_t??? Jens Gustedt <jens.gustedt@loria.fr> - 2012-02-12 00:20 +0100
              Re: return -1 using size_t??? Devil with the China Blue Dress <chine.bleu@yahoo.com> - 2012-02-12 09:21 -0800
                Re: return -1 using size_t??? Keith Thompson <kst-u@mib.org> - 2012-02-12 12:27 -0800
                Re: return -1 using size_t??? Jeroen Mostert <jmostert@xs4all.nl> - 2012-02-12 22:17 +0100
                Re: return -1 using size_t??? Devil with the China Blue Dress <chine.bleu@yahoo.com> - 2012-02-12 15:10 -0800
                Re: return -1 using size_t??? Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-02-13 03:11 -0800
                Re: return -1 using size_t??? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-12 23:25 +0000
                Re: return -1 using size_t??? Jeroen Mostert <jmostert@xs4all.nl> - 2012-02-13 07:46 +0100
                Re: return -1 using size_t??? Ike Naar <ike@sverige.freeshell.org> - 2012-02-13 10:27 +0000
                Re: return -1 using size_t??? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-13 12:36 +0000
                Re: return -1 using size_t??? Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2012-02-13 10:26 -0700
                Re: return -1 using size_t??? Ike Naar <ike@iceland.freeshell.org> - 2012-02-14 00:18 +0000
                Re: return -1 using size_t??? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-14 00:29 +0000
                Re: return -1 using size_t??? Devil with the China Blue Dress <chine.bleu@yahoo.com> - 2012-02-13 16:37 -0800
                Re: return -1 using size_t??? Angel <angel+news@spamcop.net> - 2012-02-13 11:47 +0000
                Re: return -1 using size_t??? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-13 12:54 +0000
                Re: return -1 using size_t??? Angel <angel+news@spamcop.net> - 2012-02-13 14:30 +0000
                Re: return -1 using size_t??? Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-02-22 01:53 +0200
                Re: return -1 using size_t??? James Kuyper <jameskuyper@verizon.net> - 2012-02-13 12:11 -0500
                Re: return -1 using size_t??? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-13 17:28 +0000
                Re: return -1 using size_t??? James Kuyper <jameskuyper@verizon.net> - 2012-02-13 13:08 -0500
                Re: return -1 using size_t??? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-13 23:06 +0000
                Re: return -1 using size_t??? William Ahern <william@wilbur.25thandClement.com> - 2012-02-13 14:39 -0800
                Re: return -1 using size_t??? Keith Thompson <kst-u@mib.org> - 2012-02-13 14:59 -0800
                Re: return -1 using size_t??? Jens Gustedt <jens.gustedt@loria.fr> - 2012-02-12 22:17 +0100
                Re: return -1 using size_t??? Devil with the China Blue Dress <chine.bleu@yahoo.com> - 2012-02-12 15:06 -0800
                Re: return -1 using size_t??? Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-02-12 18:12 -0500
                Re: return -1 using size_t??? Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-02-22 02:15 +0200
  Re: return -1 using size_t??? Barry Schwarz <schwarzb@dqel.com> - 2012-02-11 14:27 -0800
    Re: return -1 using size_t??? Keith Thompson <kst-u@mib.org> - 2012-02-11 17:34 -0800

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