Path: ...!weretis.net!feeder9.news.weretis.net!feeder8.news.weretis.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: olcott Newsgroups: comp.theory,sci.logic Subject: Re: D correctly simulated by pure function H cannot possibly reach its, own line 06 --- Dishonest? Date: Sun, 26 May 2024 09:13:04 -0500 Organization: A noiseless patient Spider Lines: 42 Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Sun, 26 May 2024 16:13:05 +0200 (CEST) Injection-Info: dont-email.me; posting-host="b67ec24a85de95a55e6b4d0cc81926c3"; logging-data="3613483"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX19j+MPgBYomt/hO9Ml069z8" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:qHHgIazrHDYclHccEcsMYo/f83g= Content-Language: en-US In-Reply-To: Bytes: 3587 On 5/26/2024 6:43 AM, Richard Damon wrote: typedef int (*ptr)(); // ptr is pointer to int function in C 00 int H(ptr p, ptr i); 01 int D(ptr p) 02 { 03 int Halt_Status = H(p, p); 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 } > Because, as I have said, the answer and reasoning changes depending on > what you acknowledged are the implications of your stipulations. For > instance, if your actual understanding of being a "Pure Function" is > that the program is the equivalent of a Turing Machine, then we need to > add a strictness to the definition that isn't normally used for just > "Pure Functions", like accessing value of registers like the program > counter or stack pointer might not be allowed in some cases. (which > breaks you H). > Since we can see (and you already agreed) that D correctly simulated by pure simulator H remains stuck in infinite recursive simulation then we also know that D never reaches its own line 06 and halts in less than an infinite number of correctly simulated steps. This is what I had in mind all along. Because I am a relatively terrible communicator it takes me a very long time to translate my intuitions into simple words. -- Copyright 2024 Olcott "Talent hits a target no one else can hit; Genius hits a target no one else can see." Arthur Schopenhauer