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

Groups > comp.lang.c > #12914

Re: Array of Integers ?

Show all headers | View raw

Chad <cdalten@gmail.com> writes:
[...]
> What about the following...
>
> http://67.40.109.61/torek/c/expr.html
>
> And I quote..
>
> "Array objects have a special, fundamental rule in C.  This rule is
> essentially arbitrary, and simply must be memorized.  It falls out
> from a key fact: C does not have array values.  (There is one
> exception to this, which I will save for later.)  C does have array
> objects -- just the values are missing.  For instance, int a[5];
> declares an ordinary array containing five ints. Logically, the
> ‘value’ of this array ought to be the five int values stored in that
> array -- but it is not.  Instead, the ‘value’ of the array is a
> pointer to the first element of that array. "
>
> The point being that, if I understand correctly, C does not have
> 'array of integers'. Instead, at least according to the former
> comp.lang.c regular on here, the language has 'array objects'.

I find the quoted text misleading at best.

C does have array values; it just doesn't let you manipulate them
directly in most cases.  The standard's definition of the word
"value" (C99 3.17) is "precise meaning of the contents of an object
when interpreted as having a specific type".  Nothing in that
definition excludes arrays.  Given:

    int arr[5];

the value of arr consists of the values of its 5 elements,
interpreted as having type "int[5]".  When you store something
into an array object, that object has a value, and that value is
an array value.

The relevant rule (stated in C99 6.3.2.1p3) is that an expression
of array type is implicitly converted to a (non-lvalue) pointer to
the array object's first element -- *unless* the array expression
is the operand of a unary "&" (address-of) or of "sizeof", or is
a string literal in an initializer used to initialize an array;
in those cases, an array expression really is an array expression.

Note that when we refer to "an array", we generally mean "an object
of array type", or equivalently "an array object".

arr, as defined above is an array object (of type int[5]).  Like any
array object, it is an array of objects (those objects happen to
be of type int).  More precisely, it's an array of integers (an
array of longs, or of chars, would also be an array of integers).
Even more precisely, it's an array of ints.

-- 
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"

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

Thread

Array of Integers ? arnuld <sunrise@invalid.address> - 2011-11-08 07:51 +0000
  Re: Array of Integers ? Ike Naar <ike@iceland.freeshell.org> - 2011-11-08 08:11 +0000
  Re: Array of Integers ? jacob navia <jacob@spamsink.net> - 2011-11-08 09:14 +0100
    Re: Array of Integers ? Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-11-08 00:23 -0800
      Re: Array of Integers ? pete <pfiland@mindspring.com> - 2011-11-08 04:07 -0500
    Re: Array of Integers ? tom st denis <tom@iahu.ca> - 2011-11-08 06:23 -0800
      Re: Array of Integers ? "Scott Fluhrer" <sfluhrer@ix.netcom.com> - 2011-11-08 10:08 -0500
      Re: Array of Integers ? Noob <root@127.0.0.1> - 2011-11-08 16:25 +0100
        Re: Array of Integers ? bks@panix.com (Bradley K. Sherman) - 2011-11-08 15:39 +0000
        Re: Array of Integers ? Keith Thompson <kst-u@mib.org> - 2011-11-08 13:48 -0800
          Re: Array of Integers ? Keith Thompson <kst-u@mib.org> - 2011-11-09 19:34 -0800
      Re: Array of Integers ? Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-11-08 06:59 -0800
      Re: Array of Integers ? jacob navia <jacob@spamsink.net> - 2011-11-08 22:48 +0100
    Re: Array of Integers ? Chad <cdalten@gmail.com> - 2011-11-08 07:12 -0800
      Re: Array of Integers ? pete <pfiland@mindspring.com> - 2011-11-08 11:49 -0500
      Re: Array of Integers ? James Kuyper <jameskuyper@verizon.net> - 2011-11-08 12:13 -0500
      Re: Array of Integers ? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-11-08 21:45 +0000
        Re: Array of Integers ? James Kuyper <jameskuyper@verizon.net> - 2011-11-08 16:48 -0500
          Re: Array of Integers ? Keith Thompson <kst-u@mib.org> - 2011-11-08 14:25 -0800
          Re: Array of Integers ? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-11-08 22:42 +0000
        Re: Array of Integers ? Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2011-11-10 12:01 +0200
          Re: Array of Integers ? Keith Thompson <kst-u@mib.org> - 2011-11-10 03:14 -0800
            Re: Array of Integers ? Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2011-11-10 17:41 +0200
              Re: Array of Integers ? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-11-10 16:44 +0000
                Re: Array of Integers ? Keith Thompson <kst-u@mib.org> - 2011-11-10 10:59 -0800
                Re: Array of Integers ? Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2011-11-11 17:49 +0200
      Re: Array of Integers ? Keith Thompson <kst-u@mib.org> - 2011-11-08 14:00 -0800
        Re: Array of Integers ? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-11-09 00:57 +0000
          Re: Array of Integers ? pete <pfiland@mindspring.com> - 2011-11-09 00:05 -0500
            Re: Array of Integers ? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-11-09 11:06 +0000
              Re: Array of Integers ? Keith Thompson <kst-u@mib.org> - 2011-11-09 13:36 -0800
                Re: Array of Integers ? Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-25 00:45 -0800
                Re: Array of Integers ? Keith Thompson <kst-u@mib.org> - 2012-01-25 02:56 -0800
              Re: Array of Integers ? pete <pfiland@mindspring.com> - 2011-11-09 18:34 -0500
                Re: Array of Integers ? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-11-10 00:57 +0000
          Re: Array of Integers ? Keith Thompson <kst-u@mib.org> - 2011-11-08 22:14 -0800
            Re: Array of Integers ? Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-25 01:46 -0800
  Re: Array of Integers ? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2011-11-08 01:39 -0800
    Re: Array of Integers ? Keith Thompson <kst-u@mib.org> - 2011-11-08 14:05 -0800
  Re: Array of Integers ? James Kuyper <jameskuyper@verizon.net> - 2011-11-08 06:19 -0500

csiph-web