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

Groups > comp.lang.c > #75138

Re: Pointers: misunderstanding

Show all headers | View raw

Alla _ <modelling.data@gmail.com> writes:

I'll just comment on a couple of things so far not commented on...
<snip>
> I don't test for zero, though I should have. True. May I skip this for
> now?

Yes -- you certainly don't want to test for zero.  Just remember only to
make pointers in the range &array[0] to &array[size_of_the_array] and
that the last one does not point to an element of the array -- it points
"just after".

<snip>
>>EEK!  temp is a pointer you have not set to point anywhere.  *temp is
>>therefore what we call "undefined behaviour".  But what type is
>>*pointer_1?  What sort of variable should you use to hold something of
>>that type?
>
>>>                 *pointer_1 = *pointer_2;
>>>                 *pointer_2 = *temp;
>>>            }
>>>            pointer_1++; 
>
> *pointer_1 has a type of a pointer to an integer, as pointer_2 and
> temp.

No.  *pointer_1 has type int.

> Do you mean that to declare *temp I need to allocate a memory for it with 
> malloc?

No, you don't need a pointer here at all.  You can, I'm sure, come up
with a way to swap *pointer_1 and *pointer_2 without using another
pointer.

-- 
Ben.

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

Thread

Pointers: misunderstanding Alla _ <modelling.data@gmail.com> - 2015-11-05 09:09 -0800
  Re: Pointers: misunderstanding Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-05 17:44 +0000
    Re: Pointers: misunderstanding Alla _ <modelling.data@gmail.com> - 2015-11-06 00:49 -0800
      Re: Pointers: misunderstanding Philip Lantz <prl@canterey.us> - 2015-11-06 03:01 -0800
        Re: Pointers: misunderstanding Alla _ <modelling.data@gmail.com> - 2015-11-06 03:09 -0800
  Re: Pointers: misunderstanding Barry Schwarz <schwarzb@dqel.com> - 2015-11-05 11:40 -0800
  Re: Pointers: misunderstanding Alla _ <modelling.data@gmail.com> - 2015-11-06 03:08 -0800
    Re: Pointers: misunderstanding Richard Heathfield <rjh@cpax.org.uk> - 2015-11-06 11:33 +0000
    Re: Pointers: misunderstanding Keith Thompson <kst-u@mib.org> - 2015-11-06 08:53 -0800
  Re: Pointers: misunderstanding Philip Lantz <prl@canterey.us> - 2015-11-06 03:16 -0800
    Re: Pointers: misunderstanding Alla _ <modelling.data@gmail.com> - 2015-11-06 03:30 -0800
      Re: Pointers: misunderstanding Alla _ <modelling.data@gmail.com> - 2015-11-06 03:32 -0800
        Re: Pointers: misunderstanding Alla _ <modelling.data@gmail.com> - 2015-11-06 04:58 -0800
          Re: Pointers: misunderstanding Keith Thompson <kst-u@mib.org> - 2015-11-06 09:00 -0800
            Re: Pointers: misunderstanding Alla _ <modelling.data@gmail.com> - 2015-11-06 09:25 -0800
            Re: Pointers: misunderstanding supercat@casperkitty.com - 2015-11-06 10:07 -0800
              Re: Pointers: misunderstanding Keith Thompson <kst-u@mib.org> - 2015-11-06 12:31 -0800
              Re: Pointers: misunderstanding Philip Lantz <prl@canterey.us> - 2015-11-06 20:08 -0800
        Re: Pointers: misunderstanding Alla _ <modelling.data@gmail.com> - 2015-11-06 04:59 -0800
      Re: Pointers: misunderstanding Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-06 13:06 +0000
        Re: Pointers: misunderstanding Alla _ <modelling.data@gmail.com> - 2015-11-06 08:50 -0800
          Re: Pointers: misunderstanding Richard Heathfield <rjh@cpax.org.uk> - 2015-11-06 17:00 +0000
            Re: Pointers: misunderstanding Alla _ <modelling.data@gmail.com> - 2015-11-06 09:17 -0800
              Re: Pointers: misunderstanding Richard Heathfield <rjh@cpax.org.uk> - 2015-11-06 17:22 +0000
                Re: Pointers: misunderstanding Alla _ <modelling.data@gmail.com> - 2015-11-06 09:29 -0800
              Re: Pointers: misunderstanding Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-06 17:53 +0000
            Re: Pointers: misunderstanding Alla _ <modelling.data@gmail.com> - 2015-11-06 09:22 -0800
              Re: Pointers: misunderstanding Richard Heathfield <rjh@cpax.org.uk> - 2015-11-06 17:24 +0000
                Re: Pointers: misunderstanding Alla _ <modelling.data@gmail.com> - 2015-11-06 09:33 -0800
                Re: Pointers: misunderstanding Richard Heathfield <rjh@cpax.org.uk> - 2015-11-06 18:29 +0000
                Re: Pointers: misunderstanding Alla _ <modelling.data@gmail.com> - 2015-11-06 23:42 -0800
            Re: Pointers: misunderstanding Philip Lantz <prl@canterey.us> - 2015-11-06 20:24 -0800
          Re: Pointers: misunderstanding Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-06 17:51 +0000
            Re: Pointers: misunderstanding Alla _ <modelling.data@gmail.com> - 2015-11-06 23:37 -0800
              Re: Pointers: misunderstanding Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-07 13:36 +0000
                Re: Pointers: misunderstanding Alla _ <modelling.data@gmail.com> - 2015-11-07 08:17 -0800
                Re: Pointers: misunderstanding Philip Lantz <prl@canterey.us> - 2015-11-07 12:04 -0800
    Re: Pointers: misunderstanding Keith Thompson <kst-u@mib.org> - 2015-11-06 08:55 -0800
      Re: Pointers: misunderstanding Alla _ <modelling.data@gmail.com> - 2015-11-06 09:23 -0800
  Re: Pointers: misunderstanding Philip Lantz <prl@canterey.us> - 2015-11-06 03:26 -0800
  Re: Pointers: misunderstanding Alla _ <modelling.data@gmail.com> - 2015-11-06 23:48 -0800
    Re: Pointers: misunderstanding Barry Schwarz <schwarzb@dqel.com> - 2015-11-07 00:35 -0800
  Re: Pointers: misunderstanding Alla _ <modelling.data@gmail.com> - 2015-11-06 23:48 -0800
    Re: Pointers: misunderstanding Keith Thompson <kst-u@mib.org> - 2015-11-07 12:24 -0800

csiph-web