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From: wij <wyniijj5@gmail.com>
Newsgroups: comp.theory
Subject: Re: Every sufficiently competent C programmer knows
Date: Wed, 12 Mar 2025 02:33:15 +0800
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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=20
> > the halt7.c file (along with DDD) that PO provides links to from=20
> > time to time.=C2=A0 However it's not very illuminating due to=20
> > bugs/design errors/misunderstandings which only serve to=20
> > obfuscate PO's errors in thinking.
>=20
> [I've now seen the code. Oh deary deary me.]
>=20
> Thank you for a spirited attempt to be cogent - or at least as=20
> cogent as it is possible to be in the circumstances!
>=20
> I think PO's first step must be to demonstrate that HHH()=20
> correctly diagnoses some easy functions, such as these:
>=20
> int rha(unsigned int i)
> {
> =C2=A0=C2=A0 while(--i > 0)while(--i > 0);
> =C2=A0=C2=A0 return 0;
> }
>=20
> int rhb(unsigned int i)
> {
> =C2=A0=C2=A0 if(i > 0)
> =C2=A0=C2=A0 {
> =C2=A0=C2=A0=C2=A0=C2=A0 rhb(i/10);
> =C2=A0=C2=A0 }
> =C2=A0=C2=A0 return putchar(i + '0');
> }
>=20
> int rhc(unsigned int i)
> {
> =C2=A0=C2=A0 typedef int(*pf)(unsigned int);
> =C2=A0=C2=A0 pf arr[3] =3D {rha, rhb, rhc};
> =C2=A0=C2=A0 return arr[i % 3];
> }
>=20
> and other such obvious tests.
>=20
> HHH(), the procedure that decides whether a program halts, is=20
> required to work for all programs and all inputs. Does it work on=20
> those cited above? I'm guessing it doesn't.
>=20

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