Sujet : Re: Every D correctly simulated by H never reaches its final state and halts
De : mikko.levanto (at) *nospam* iki.fi (Mikko)
Groupes : comp.theoryDate : 19. May 2024, 12:37:11
Autres entêtes
Organisation : -
Message-ID : <v2ckon$3bc16$1@dont-email.me>
References : 1 2 3 4 5 6
User-Agent : Unison/2.2
On 2024-05-18 14:38:53 +0000, olcott said:
On 5/18/2024 4:45 AM, Mikko wrote:
On 2024-05-17 15:55:03 +0000, olcott said:
On 5/17/2024 4:08 AM, Mikko wrote:
On 2024-05-17 07:25:52 +0000, Fred. Zwarts said:
Op 17.mei.2024 om 03:15 schreef olcott:
The following is self-evidently true on the basis of the
semantics of the C programming language.
typedef int (*ptr)(); // ptr is pointer to int function
00 int H(ptr x, ptr x);
01 int D(ptr x)
02 {
03 int Halt_Status = H(x, x);
04 if (Halt_Status)
05 HERE: goto HERE;
06 return Halt_Status;
07 }
08
09 int main()
10 {
11 H(D,D);
12 return 0;
13 }
In the above case a simulator is an x86 emulator that correctly
emulates at least one of the x86 instructions of D in the order
specified by the x86 instructions of D.
This may include correctly emulating the x86 instructions of H
in the order specified by the x86 instructions of H thus calling
H(D,D) in recursive simulation.
Any H/D pair matching the above template where
D(D) is simulated by the same H(D,D) that it calls
cannot possibly reach its own line 06 and halt.
*This is a simple software engineering verified fact*
Note that olcott defines 'verified fact' as 'proven fact', but he is unable to show the proof. So, it must be read as 'my belief'.
A "proven fact" without a proof is not worse than a "verified fact"
without a verification.
*I updated my wording*
It is self-evidently true to anyone having sufficient knowledge
of the semantics of the C programming language.
No, it is not. I would know if it were.
If you do not understand that a single valid counter-example
would refute my claim then you don't know enough about proofs.
Your claim
It is self-evidently true to anyone having sufficient knowledge
of the semantics of the C programming language.
is a little unclear about the meaning of "It" but I think it
is false for any reasonable interpretation. Can I call myself
a counter-example?
-- Mikko