In article <gjohnsonCLywLL.A00@netcom.com> gjohnson@netcom.com (Serendipitous Freelance Hacker) writes:

> int i = 0;
> if( NULL == 0 && NULL != i ) LaughAtANSI();

I don't get it.

I can see no way that LaughAtANSI will ever be called in this example.

If NULL is a synonym for 0, there's no problem.
If you're one of those people who would like NULL to be implemented
as (void*)0, then the fragment will not compile, there being no
generalized conversions between int and pointer.
--
    --Andrew Koenig
      ark@research.att.com

In article <gjohnsonCLywLL.A00@netcom.com> gjohnson@netcom.com
(Serendipitous Freelance Hacker) writes:

|> In article <CJKMF1.3Co@tempel.research.att.com> ark@tempel.research.att.com (Andrew Koenig) writes:
|> >In article <2h1sm0INN67s@umbc7.umbc.edu> squire@umbc.edu (Mr. Jon S. Squire) writes:

|> >> But, but, but! You do not seem to understand that null pointers may be
|> >> non zero. This is implementation dependent, as every 'coder' should
|> >> understand.

|> >Regardless of representation, every null pointer is required to compare
|> >equal to (literal integral) zero.

|> //...
|> int i = 0;
|> if( NULL == 0 && NULL != i ) LaughAtANSI();
|> //...

As written, the above must be false.  NULL is *not* a null pointer, at
least not currently.  NULL is an integer constant 0, which will
implicitly convert to a null pointer constant in a pointer context.

I presume that what was meant was something like:

 char*  p = NULL ;
 int  i = 0 ;
 if ( p == 0 && p != i ) ...

However, this is simply illegal.  You cannot compare a pointer to an
integer, anymore than you can compare apples to oranges.

Whether you can convert a pointer to an integer is implementation
defined.  (I know of implementations where pointers are 48 bits, but
the largest integer is only 32 bits.)  For implementations where you
*can* do this conversion, whether the following expression is true or
false *is* undefined:

 char*  p = 0 ;
 if ( int( p ) == 0 ) ...

--
James Kanze                       email: kanze@lts.sel.alcatel.de
GABI Software, Sarl., 8 rue du Faisan, F-67000 Strasbourg, France
Conseils en informatique industrielle --
                   -- Beratung in industrieller Datenverarbeitung

In article <CJKMF1.3Co@tempel.research.att.com> ark@tempel.research.att.com (Andrew Koenig) writes:
>In article <2h1sm0INN67s@umbc7.umbc.edu> squire@umbc.edu (Mr. Jon S. Squire) writes:
>
>> But, but, but! You do not seem to understand that null pointers may be
>> non zero. This is implementation dependent, as every 'coder' should
>> understand.
>
>Regardless of representation, every null pointer is required to compare
>equal to (literal integral) zero.

//...
int i = 0;
if( NULL == 0 && NULL != i ) LaughAtANSI();
//...

--
Gary Johnson (Freelance Hacker) gjohnson@netcom.com "Public private keys?!"