dev-cpp-users

[Dev-C++] Addresses and Pointers

[<and...@su...>]

Dear Users,

Please consider the following codes:

/* p1.c */
...
1-int x=16, *p;
2-
3-p=&x;
5-printf(“%p\n”, *&p);
...

/* p2.c */
...
1-int x=16, *p;
2-
3-p=&x;
5-printf(“%d\n”, &*p);
...

/* p3.c */
...
1-int x=16, *p;
2-
3-p=&x;
4-printf(“%p\n”, *&x);
...

/* p4.c */
...
1-int x=16, *p;
2-
3-p=&x;
4-printf(“%d\n”, &*x);
...

Theese pieces of code were presented to show the relashionship between:
  -&x/p and x/*p
  -hexadecimal conversion from one value to another (%p and %d)
  - &* and *& cancel themselves

--->But p4.c isn´t working. The compiler is presenting the following error
message:
   "Invalid type argument of ´unary´"


Regards
Andre

Re: [Dev-C++] Addresses and Pointers

[w.y. <yok...@ve...>]

André Macário Barros wrote:
> 
> /* p4.c */
> ...
> 1-int x=16, *p;
> 2-
> 3-p=&x;
> 4-printf(“%d\n”, &*x);


>   - &* and *& cancel themselves
> 
> --->But p4.c isn´t working. The compiler is presenting the following error
> message:
>    "Invalid type argument of ´unary´"

The way I read &*x is first x is dereferenced, so it becomes

&16

and you cannot use the 'address of' operator & on a number, 16,
so you get an error.

Re: [Dev-C++] Addresses and Pointers

[w.y. <yok...@ve...>]

"w.y." wrote:
> 
> André Macário Barros wrote:
> >
> > /* p4.c */
> > ...
> > 1-int x=16, *p;
> > 2-
> > 3-p=&x;
> > 4-printf(“%d\n”, &*x);
> 
> >   - &* and *& cancel themselves
> >

Ignore what I said previously. I read it wrong. :)

RE: [Dev-C++] Addresses and Pointers

[Ioannis V. <iv...@em...>]

> -----Original Message-----
> From: dev...@li...=20
> [mailto:dev...@li...] On Behalf=20
> Of Andr? Macario Barros
> Sent: Tuesday, August 26, 2003 6:52 AM
> To: Dev-Cpp-Users
> Subject: [Dev-C++] Addresses and Pointers
>=20
>=20
> Dear Users,
>=20
> Please consider the following codes:
>=20
> /* p1.c */
> ...
> 1-int x=3D16, *p;
> 2-
> 3-p=3D&x;
> 5-printf(=93%p\n=94, *&p);



I just got a headache. Let's skip the others and concentrate on the =
point
you ask.



=20
> /* p4.c */
> ...
> 1-int x=3D16, *p;
> 2-
> 3-p=3D&x;
> 4-printf(=93%d\n=94, &*x);
> ...
> --->But p4.c isn=B4t working. The compiler is presenting the=20
> following error
> message:
>    "Invalid type argument of =B4unary=B4"



x is a variable of type int. This means, that the dereference operator *
can't be applied to it. * can be applied only to pointers.






Ioannis Vranos
=20
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