Path: ...!weretis.net!feeder9.news.weretis.net!news.quux.org!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail From: olcott Newsgroups: comp.theory,comp.lang.c,comp.lang.c++ Subject: Re: Every sufficiently competent C programmer knows --- Paraphrase of Sipser's agreement Followup-To: comp.theory Date: Sat, 15 Mar 2025 16:27:00 -0500 Organization: A noiseless patient Spider Lines: 111 Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Date: Sat, 15 Mar 2025 22:27:03 +0100 (CET) Injection-Info: dont-email.me; posting-host="442a9ec1ae8b0ed609e933f76503e6e9"; logging-data="381848"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+IhnmNqrlJL3kit+AA/dnI" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:ZYRK43Ykh9UG4uhmblosCfQKbmU= Content-Language: en-US X-Antivirus-Status: Clean X-Antivirus: Norton (VPS 250315-4, 3/15/2025), Outbound message In-Reply-To: Bytes: 5804 On 3/15/2025 5:12 AM, Mikko wrote: > On 2025-03-14 14:39:30 +0000, olcott said: > >> On 3/14/2025 4:03 AM, Mikko wrote: >>> On 2025-03-13 20:56:22 +0000, olcott said: >>> >>>> On 3/13/2025 4:22 AM, Mikko wrote: >>>>> On 2025-03-13 00:36:04 +0000, olcott said: >>>>> >>>>>> >>>>>> void DDD() >>>>>> { >>>>>>    HHH(DDD); >>>>>>    return; >>>>>> } >>>>>> >>>>>> int DD() >>>>>> { >>>>>>    int Halt_Status = HHH(DD); >>>>>>    if (Halt_Status) >>>>>>      HERE: goto HERE; >>>>>>    return Halt_Status; >>>>>> } >>>>>> >>>>>> When HHH correctly emulates N steps of the >>>>>> above functions none of them can possibly reach >>>>>> their own "return" instruction and terminate normally. >>>>> >>>>> Nevertheless, assuming HHH is a decider, Infinite_Loop and >>>>> Infinite_Recursion >>>>> specify a non-terminating behaviour, DDD specifies a terminating >>>>> behaviour >>>> >>>> _DDD() >>>> [00002172] 55         push ebp      ; housekeeping >>>> [00002173] 8bec       mov  ebp,esp  ; housekeeping >>>> [00002175] 6872210000 push 00002172 ; push DDD >>>> [0000217a] e853f4ffff call 000015d2 ; call HHH(DDD) >>>> [0000217f] 83c404     add  esp,+04 >>>> [00002182] 5d         pop  ebp >>>> [00002183] c3         ret >>>> Size in bytes:(0018) [00002183] >>>> >>>> What is the sequence of machine language >>>> instructions of DDD emulated by HHH such that DDD >>>> reaches its machine address 00002183? >>> >>> Irrelevant off-topic distraction. >> >> Proving that you don't have a clue that Rice's Theorem >> is anchored in the behavior that its finite string input >> specifies. The depth of your knowledge is memorizing >> quotes from textbooks. > > Another irrelevant off-topic distraction, this time involving > a false claim. > > One can be a competent C programmer without knowing anyting about Rice's > Theorem. > YES. > Rice's Theorem is about semantic properties in general, not just > behaviours. > The unsolvability of the halting problem is just a special case. > A property about Turing machines can be represented as the language of all Turing machines, encoded as strings, that satisfy that property. http://kilby.stanford.edu/~rvg/154/handouts/Rice.html Does THE INPUT TO simulating termination analyzer HHH encode a C function that reaches its "return" instruction [WHEN SIMULATED BY HHH] (The definition of simulating termination analyzer) ??? If simulating halt decider H correctly simulates its input D until H correctly determines that its simulated D would never stop running unless aborted then H can abort its simulation of D and correctly report that D specifies a non-halting sequence of configurations. If emulating termination analyzer H emulates its input finite string D of x86 machine language instructions according to the semantics of the x86 programming language until H correctly determines that this emulated D cannot possibly reach its own "ret" instruction in any finite number of correctly emulated steps then H can abort its emulation of input D and correctly report that D specifies a non-halting sequence of configurations. > Memorizing quotes from textbooks is useful for practical purposes but > if it is too hard for you there are other ways. > The whole X represents TM X that halts on its input is inaccurate. If you did not merely learn-by-rote you would already know this. *Input Y to TM Z specifies a TM that halts when directly measured by Z* -- Copyright 2025 Olcott "Talent hits a target no one else can hit; Genius hits a target no one else can see." Arthur Schopenhauer