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Re: unsigned int

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Les Cargill <lcargill99@comcast.com> writes:

> David Brown wrote:
>> On 01/08/16 16:59, Les Cargill wrote:
>>> David Brown wrote:
>>>> On 31/07/16 19:40, Osmium wrote:
>>>>
>>>>>
>>>>> A novice would naturally think that char was signed by default, the same
>>>>> as an int.  It is not, the default is chosen by the compiler writer.
>>>>> Among other things, this has ramifications in bit shifting within
>>>>> characters,.
>>>>
>>>> A novice may equally well think that a char was /unsigned/ by default,
>>>> since the obvious interpretation of "char" is "character", such as
>>>> letters, digits, etc. - and the concept of a "negative character" is
>>>> totally meaningless.
>>>
>>> So then they must learn that a char is a specialization of an int. And
>>> ints default to signed because the integers are both negative and
>>> positive in mathematics.
>>
>> But "char" is not a "specialisation of an int" in C - they have
>> different properties, and neither is a subset of the other.  And while
>> "int" is signed in C, "char" is not necessarily signed.
>
> So I'm calling that a swing and a miss. A char is an int that is
> constrained to be less bits. All chars have exactly the same semantics
> as ints. Default char in 'C' is always unsigned unless you use compiler
> options to make it otherwise, or unless the compiler defaults it for
> you.

Quite a lot of that is wrong.  A char is not an int with fewer bits.
For one thing, it might have the same number of bits, and, even when it
has fewer, it may be unsigned making it very unlike an int with fewer
bits.  That means that char does not always have the same semantics as
int.

The last bit reads oddly but ends up being right because it says that
char is always unsigned except when it isn't.

<snip>
> The problem is that there's a great and powerful simplifying assumption
> in play - 'a' is exactly equivalent to the integer 0xa1. I find this
> quite comforting; it's a simple rule.

In C, the character constant 'a' certainly has type int, but you can't
say what the value is.  0xa1 is a possible value but where did that come
from?  (If you'd said 0x61 (ASCII) or 0x81 (EBCDIC) I would not have been
too surprised.)

>> I would like a type "byte" which
>> represents raw data in memory - "byte *" would be used instead of "void
>> *" in C, and also in many cases where "char *" is used.
>
> I rather like "void *" because void is the identity un-type - it is a
> type with zero semantic information about it. A void * is a pointer for
> the sake of a pointer, used only as an r-value in order to assign or
> cast to a richer type.

I think I know what you are getting at (basically that you can't do much
with a void *) but in C you can have l-value expressions of void * type.

<snip>
-- 
Ben.

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Re: unsigned int "Osmium" <r124c4u102@comcast.net> - 2016-07-31 12:40 -0500
  Re: unsigned int David Brown <david.brown@hesbynett.no> - 2016-08-01 11:01 +0200
    Re: unsigned int James Kuyper <jameskuyper@verizon.net> - 2016-08-01 10:15 -0400
    Re: unsigned int Les Cargill <lcargill99@comcast.com> - 2016-08-01 09:59 -0500
      Re: unsigned int David Brown <david.brown@hesbynett.no> - 2016-08-01 17:21 +0200
        Re: unsigned int Keith Thompson <kst-u@mib.org> - 2016-08-01 09:55 -0700
          Re: unsigned int David Brown <david.brown@hesbynett.no> - 2016-08-01 22:42 +0200
            Re: unsigned int supercat@casperkitty.com - 2016-08-01 14:18 -0700
        Re: unsigned int Les Cargill <lcargill99@comcast.com> - 2016-08-01 13:11 -0500
          Re: unsigned int Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-01 19:46 +0100
            Re: unsigned int Les Cargill <lcargill99@comcast.com> - 2016-08-01 18:20 -0500
              Re: unsigned int David Brown <david.brown@hesbynett.no> - 2016-08-02 10:18 +0200
                Re: unsigned int Les Cargill <lcargill99@comcast.com> - 2016-08-02 09:35 -0500
                Re: unsigned int Keith Thompson <kst-u@mib.org> - 2016-08-02 08:00 -0700
                Re: unsigned int Les Cargill <lcargill99@comcast.com> - 2016-08-02 11:12 -0500
                Re: unsigned int David Brown <david.brown@hesbynett.no> - 2016-08-02 17:11 +0200
                Re: unsigned int Les Cargill <lcargill99@comcast.com> - 2016-08-02 11:55 -0500
                Re: unsigned int supercat@casperkitty.com - 2016-08-02 10:16 -0700
                Re: unsigned int David Brown <david.brown@hesbynett.no> - 2016-08-03 14:02 +0200
                Re: unsigned int Keith Thompson <kst-u@mib.org> - 2016-08-03 08:58 -0700
                Re: unsigned int James Kuyper <jameskuyper@verizon.net> - 2016-08-02 13:57 -0400
                Re: unsigned int Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-02 19:30 +0100
                Re: unsigned int Keith Thompson <kst-u@mib.org> - 2016-08-02 11:38 -0700
                Re: unsigned int David Brown <david.brown@hesbynett.no> - 2016-08-03 14:12 +0200
                Re: unsigned int David Brown <david.brown@hesbynett.no> - 2016-08-03 13:45 +0200
          Re: unsigned int Keith Thompson <kst-u@mib.org> - 2016-08-01 12:02 -0700
            Re: unsigned int David Brown <david.brown@hesbynett.no> - 2016-08-01 23:01 +0200

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