Re: Every sufficiently competent C programmer knows

On Tue, 2025-03-11 at 18:23 +0000, Richard Heathfield wrote:

On 11/03/2025 17:42, Mike Terry wrote:

Finally, if you really want to see the actual HHH code, its in> > the halt7.c file (along with DDD) that PO provides links to from> > time to time.  However it's not very illuminating due to> > bugs/design errors/misunderstandings which only serve to> > obfuscate PO's errors in thinking.

 [I've now seen the code. Oh deary deary me.]
 Thank you for a spirited attempt to be cogent - or at least as> cogent as it is possible to be in the circumstances!
 I think PO's first step must be to demonstrate that HHH()> correctly diagnoses some easy functions, such as these:
 int rha(unsigned int i)
{
   while(--i > 0)while(--i > 0);
   return 0;
}
 int rhb(unsigned int i)
{
   if(i > 0)
   {
     rhb(i/10);
   }
   return putchar(i + '0');
}
 int rhc(unsigned int i)
{
   typedef int(*pf)(unsigned int);
   pf arr[3] = {rha, rhb, rhc};
   return arr[i % 3];
}
 and other such obvious tests.
 HHH(), the procedure that decides whether a program halts, is> required to work for all programs and all inputs. Does it work on> those cited above? I'm guessing it doesn't.
 

 No TM can simulate itself. Proving HP in this way is dead end.