Re: Pointer Problem

From	Mike McCarty <mcmccarty@gmail.com>
Newsgroups	comp.lang.c++
Subject	Re: Pointer Problem
Date	2012-02-26 21:30 -0800
Organization	http://groups.google.com
Message-ID	<3478397.2346.1330320657665.JavaMail.geo-discussion-forums@vbae11> (permalink)
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On Sunday, February 26, 2012 2:41:07 PM UTC-6, Paul wrote:
> The argument
> I am opposing is that an int* cannot point to an array of ints and can
> only point to one single int. I am arguing against this because it
> breaks in so many ways the most obvious being that.. the pointer type
> does not define the pointed-to object as I think I have explained
> above.

In fact, I think that's exactly the point they're trying to make:  The conversion from 'int[10]' to 'int*' implies loss of information.  The lost information can only be resurrected via _convention_ (e.g. begin/end range pointers, etc.), not thru the type system itself.

An example:

int a[10];
int (&b)[9] = a[1];

The C++ language dictates that this is illegal syntax, despite the fact that simple analysis shows that it is perfectly reasonable and logically correct.  This is the sort of 'context' you've been referring to but this 'context' is exactly what the language does not support.  

FWIW, you can always force context upon the language, see http://codepad.org/pyZzy6Ae.  Not that I recommend it...

> This seems to be the argument against me: that int* points to a single
> int because its type is pointer to int, int(*)[10] is a pointer to an
> array of 10 ints because its pointer type is pointer to int[10] etc
> etc. As I have said this argument breaks down in many ways and thus I
> object to them saying it's incorrect that an int* points to an array.

Given only 

int* iptr = something();

all you can say definitely is that iptr either points to an object (e.g. iptr=&arr[15]) or it does not (iptr=NULL).  Everything else can only be deduced from additional external information that the int* type itself does not provide.  

If I've still managed to miss the point, you're going to have to forgive me.

Mike

Thread

Pointer Problem bintom <binoythomas1108@gmail.com> - 2012-02-16 06:51 -0800
  Re: Pointer Problem Juha Nieminen <nospam@thanks.invalid> - 2012-02-16 15:15 +0000
    Re: Pointer Problem 88888 Dihedral <dihedral88888@googlemail.com> - 2012-02-16 07:17 -0800
      Re: Pointer Problem Victor Bazarov <v.bazarov@comcast.invalid> - 2012-02-16 11:15 -0500
        Re: Pointer Problem scott@slp53.sl.home (Scott Lurndal) - 2012-02-16 17:18 +0000
          Re: Pointer Problem Victor Bazarov <v.bazarov@comcast.invalid> - 2012-02-16 13:46 -0500
            Re: Pointer Problem Mike McCarty <mcmccarty@gmail.com> - 2012-02-16 12:41 -0800
            Re: Pointer Problem scott@slp53.sl.home (Scott Lurndal) - 2012-02-16 20:45 +0000
            Re: Pointer Problem Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-02-17 01:44 -0800
    Re: Pointer Problem jt@toerring.de (Jens Thoms Toerring) - 2012-02-17 03:14 +0000
      Re: Pointer Problem Juha Nieminen <nospam@thanks.invalid> - 2012-02-17 07:23 +0000
        Re: Pointer Problem jt@toerring.de (Jens Thoms Toerring) - 2012-02-18 22:39 +0000
          Re: Pointer Problem Peter Remmers <p.remmers@expires-2011-04-30.arcornews.de> - 2012-02-20 21:07 +0100
            Re: Pointer Problem Paul <pchristor@yahoo.co.uk> - 2012-02-21 18:49 -0800
          Re: Pointer Problem Paul <pchristor@yahoo.co.uk> - 2012-02-21 18:49 -0800
            Re: Pointer Problem Juha Nieminen <nospam@thanks.invalid> - 2012-02-22 10:15 +0000
              Re: Pointer Problem Paul <pchristor@yahoo.co.uk> - 2012-02-22 07:49 -0800
                Re: Pointer Problem Leigh Johnston <leigh@i42.co.uk> - 2012-02-22 20:24 +0000
                Re: Pointer Problem Juha Nieminen <nospam@thanks.invalid> - 2012-02-23 10:36 +0000
                Re: Pointer Problem "Paul" <pchrist<nospam>or@yahoo.co.uk> - 2012-02-23 18:59 +0000
                Re: Pointer Problem Leigh Johnston <leigh@i42.co.uk> - 2012-02-23 19:15 +0000
                Re: Pointer Problem "Paul" <pchrist<nospam>or@yahoo.co.uk> - 2012-02-23 21:08 +0000
                Re: Pointer Problem Leigh Johnston <leigh@i42.co.uk> - 2012-02-23 21:17 +0000
                Re: Pointer Problem Leigh Johnston <leigh@i42.co.uk> - 2012-02-23 21:29 +0000
                Re: Pointer Problem Joshua Maurice <joshuamaurice@gmail.com> - 2012-02-23 17:06 -0800
                Re: Pointer Problem Paul <pchristor@yahoo.co.uk> - 2012-02-24 03:42 -0800
                Re: Pointer Problem Leigh Johnston <leigh@i42.co.uk> - 2012-02-24 12:33 +0000
                Re: Pointer Problem "Paul" <pchrist<nospam>or@yahoo.co.uk> - 2012-02-24 15:09 +0000
                Re: Pointer Problem Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-02-23 20:53 +0000
                Re: Pointer Problem Paul <pchristor@yahoo.co.uk> - 2012-02-24 04:11 -0800
                Re: Pointer Problem Leigh Johnston <leigh@i42.co.uk> - 2012-02-24 12:36 +0000
                Re: Pointer Problem Paul <pchristor@yahoo.co.uk> - 2012-02-24 06:07 -0800
                Re: Pointer Problem Leigh Johnston <leigh@i42.co.uk> - 2012-02-24 14:11 +0000
                Re: Pointer Problem "Paul" <pchrist<nospam>or@yahoo.co.uk> - 2012-02-24 15:49 +0000
                Re: Pointer Problem Mike McCarty <mcmccarty@gmail.com> - 2012-02-24 08:50 -0800
                Re: Pointer Problem "Paul" <pchrist<nospam>or@yahoo.co.uk> - 2012-02-24 18:47 +0000
                Re: Pointer Problem Paul <pchristor@yahoo.co.uk> - 2012-02-24 13:44 -0800
                Re: Pointer Problem Paul <pchristor@yahoo.co.uk> - 2012-02-26 12:41 -0800
                Re: Pointer Problem Mike McCarty <mcmccarty@gmail.com> - 2012-02-26 21:30 -0800
                Re: Pointer Problem Paul <pchristor@yahoo.co.uk> - 2012-02-27 06:07 -0800
                Re: Pointer Problem Mike McCarty <mcmccarty@gmail.com> - 2012-02-27 07:25 -0800
                Re: Pointer Problem Paul <pchristor@yahoo.co.uk> - 2012-02-27 08:17 -0800
                Re: Pointer Problem Mike McCarty <mcmccarty@gmail.com> - 2012-02-27 08:51 -0800
                Re: Pointer Problem Ian Collins <ian-news@hotmail.com> - 2012-02-28 07:18 +1300
                Re: Pointer Problem Paul <pchristor@yahoo.co.uk> - 2012-02-27 11:32 -0800
                Re: Pointer Problem Paul <pchristor@yahoo.co.uk> - 2012-02-27 11:32 -0800
                Re: Pointer Problem Leigh Johnston <leigh@i42.co.uk> - 2012-02-27 19:17 +0000
                Re: Pointer Problem Paul <pchristor@yahoo.co.uk> - 2012-02-27 11:49 -0800
                Re: Pointer Problem Leigh Johnston <leigh@i42.co.uk> - 2012-02-27 20:04 +0000
                Re: Pointer Problem Paul <pchristor@yahoo.co.uk> - 2012-02-27 12:55 -0800
                Re: Pointer Problem Leigh Johnston <leigh@i42.co.uk> - 2012-02-27 21:15 +0000
                Re: Pointer Problem Paul <pchristor@yahoo.co.uk> - 2012-02-27 14:26 -0800
                Re: Pointer Problem Paul <pchristor@yahoo.co.uk> - 2012-02-27 11:21 -0800
  Re: Pointer Problem SG <s.gesemann@gmail.com> - 2012-02-16 07:00 -0800
  Re: Pointer Problem LR <lruss@superlink.net> - 2012-02-16 16:49 -0500
    Re: Pointer Problem Juha Nieminen <nospam@thanks.invalid> - 2012-02-16 22:18 +0000
      Re: Pointer Problem LR <lruss@superlink.net> - 2012-02-16 23:40 -0500
        Re: Pointer Problem Juha Nieminen <nospam@thanks.invalid> - 2012-02-17 07:24 +0000
          Re: Pointer Problem LR <lruss@superlink.net> - 2012-02-17 09:48 -0500
            Re: Pointer Problem Juha Nieminen <nospam@thanks.invalid> - 2012-02-17 15:13 +0000

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