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Re: Slow -- VERY slow brain

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madamemandm@yahoo.com wrote:

> On Jun 16, 3:46 pm, "Alf P. Steinbach /Usenet" <alf.p.steinbach
> +use...@gmail.com> wrote:
>> * madamema...@yahoo.com, on 16.06.2011 22:10:
> [snip]
>> > On Jun 16, 11:51 am, "Alf P. Steinbach
>> > /Usenet"<alf.p.steinbach+use...@gmail.com>  wrote:
>> >> The standard guarantees that when x is of integral type then
>> >> unsigned(x) is congruent to x modulo 2^n where n is the number of
>> >> value representation bits in `unsigned`. No, this isn't it a quote. I
>> >> just haven't had my coffee yet so not quite able to express things
>> >> more simply, sorry.
>>
>> > That is correct, and if you do the math under the conditions I
>> > described, you find that unsigned(INT_MIN) == 1.
>>
>> $3.9.1/3 requires the same value representation for a signed type as for
>> its corresponding unsigned type.
> 
> n3092 says that they have the same object representation, not the same
> value representation.
> Which version are you getting yours from?
[...]

Actual standard [3.9.1/3]:

  For each of the signed integer types, there exists a corresponding (but 
  different) unsigned integer type: "unsigned char", "unsigned short int", 
  "unsigned int", and "unsigned long int," each of which occupies the same
  amount of storage and has the same alignment requirements (3.9) as the
  corresponding signed integer type40) ; that is, each signed integer type
  has the same object representation as its corresponding unsigned integer
  type. 

That is the sentence, you read. But read further in the same clause:

  The range of nonnegative values of a signed integer type is a subrange of 
  the corresponding unsigned integer type, and the value representation of 
  each corresponding signed/unsigned type shall be the same.

In particularm note the "and the value representation ..." part.


In draft n3291 [3.9.1/3] you find the same:

  For each of the standard signed integer types, there exists a 
  corresponding (but different) standard unsigned integer type: "unsigned 
  char", "unsigned short int", "unsigned int", "unsigned long int", and
  "unsigned long long int", each of which occupies the same amount of
  storage and has the same alignment requirements (3.11) as the 
  corresponding signed integer type45 ; that is, each signed integer type 
  has the same object representation as its corresponding unsigned integer 
  type. Likewise, for each of the extended signed integer types there exists 
  a corresponding extended unsigned integer type with the same amount of
  storage and alignment requirements. The standard and extended unsigned 
  integer types are collectively called unsigned integer types. The range of
  non-negative values of a signed integer type is a subrange of the 
  corresponding unsigned integer type, and 

    the value representation of each corresponding signed/unsigned type 
    shall be the same. [highlighting added]

  The standard signed integer types and standard unsigned integer types are
  collectively called the standard integer types, and the extended signed 
  integer types and extended unsigned integer types are collectively called 
  the extended integer types.


You might want to check n3092 again. Chances are, it also contains the 
provision about the value representation.


Best,

Kai-Uwe Bux

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Thread

Slow -- VERY slow brain "Alf P. Steinbach /Usenet" <alf.p.steinbach+usenet@gmail.com> - 2011-06-16 01:08 +0200
  Re: Slow -- VERY slow brain "Balog Pal" <pasa@lib.hu> - 2011-06-16 01:44 +0200
  Re: Slow -- VERY slow brain Puppet_Sock <puppet_sock@hotmail.com> - 2011-06-16 06:25 -0700
    Re: Slow -- VERY slow brain Noah Roberts <dont@email.me> - 2011-06-29 10:05 -0700
  Re: Slow -- VERY slow brain Keith H Duggar <duggar@alum.mit.edu> - 2011-06-16 07:00 -0700
  Re: Slow -- VERY slow brain "madamemandm@yahoo.com" <madamemandm@yahoo.com> - 2011-06-16 07:22 -0700
    Re: Slow -- VERY slow brain "madamemandm@yahoo.com" <madamemandm@yahoo.com> - 2011-06-16 07:31 -0700
      Re: Slow -- VERY slow brain "Alf P. Steinbach /Usenet" <alf.p.steinbach+usenet@gmail.com> - 2011-06-16 18:51 +0200
        Re: Slow -- VERY slow brain "madamemandm@yahoo.com" <madamemandm@yahoo.com> - 2011-06-16 13:10 -0700
          Re: Slow -- VERY slow brain "Alf P. Steinbach /Usenet" <alf.p.steinbach+usenet@gmail.com> - 2011-06-16 22:46 +0200
            Re: Slow -- VERY slow brain "madamemandm@yahoo.com" <madamemandm@yahoo.com> - 2011-06-17 07:38 -0700
              Re: Slow -- VERY slow brain Kai-Uwe Bux <jkherciueh@gmx.net> - 2011-06-17 18:06 +0200
                Re: Slow -- VERY slow brain "madamemandm@yahoo.com" <madamemandm@yahoo.com> - 2011-06-17 10:49 -0700
        Re: Slow -- VERY slow brain "Paul" <pchristor@yahoo.co.uk> - 2011-06-17 18:27 +0100
  Re: Slow -- VERY slow brain Werner <werasm@gmail.com> - 2011-06-17 01:33 -0700
    Re: Slow -- VERY slow brain Öö Tiib <ootiib@hot.ee> - 2011-06-17 07:48 -0700
      Re: Slow -- VERY slow brain Werner <werasm@gmail.com> - 2011-06-17 09:39 -0700
    Re: Slow -- VERY slow brain "Alf P. Steinbach /Usenet" <alf.p.steinbach+usenet@gmail.com> - 2011-06-17 19:59 +0200

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