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Re: [vox-tech] C - passing chars and pointer to chars
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Re: [vox-tech] C - passing chars and pointer to chars



On Sun 04 Jun 06,  9:57 AM, Ken Bloom <kbloom@gmail.com> said:
> On Sunday 04 June 2006 09:05, Peter Jay Salzman wrote:
> > On Sat 03 Jun 06, 10:27 PM, Ken Bloom <kbloom@gmail.com> said:
> > > Cue, the **Fundemental axiom of the C++ type system**, stated as
> > > follows:
> > >   A* is automaitcally convertable to B* if and only if A is a B.
> > >   (Likewise for pass by reference).
> > >
> > > (this is my own generalization though, and there may actually be
> > > exceptions)
> 
> >
> > Although this was interesting to read, it doesn't say much other than
> > to restate my observation in a more sophisticated way.
> 
> IMO, all that matters is that the axiom is the reason.
> 
> --Ken
 

Herr Godel would say that this type of thinking is why it took humanity over
2000 years to discover non-Euclidean geometry.   ;-)


BTW, "void *" seems to be an exception to the axiom:


   p@satan$ cat bar.c 
   void f( void *b );


   int main( void )
   {
           int a;
           f( &a );
           return 0;
   }
   p@satan$ gcc -W -Wall -c bar.c 
   p@satan$ 

A "int *" is convertable to "void *" even though an int isn't a void.  There
is no data type of "void" (I think), but it's still a counter example.

BTW, you mentioned that it was a generalization of the fundamental axiom of
the C++ type system -- what is the fundamental axiom?  That sounds like
something I should know, but I've never heard of it.

Pete
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