Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!olivea!tymix!cirrusl!ss262!dhesi From: dhesi%cirrusl@oliveb.ATC.olivetti.com (Rahul Dhesi) Newsgroups: comp.lang.misc Subject: Re: The Halting Problem is _not_ solvable on real com Message-ID: <3125@cirrusl.UUCP> Date: 10 May 91 19:18:48 GMT References: <2990@optima.cs.arizona.edu> <1991May10.155454.2239@maths.nott.ac.uk> Sender: news@cirrusl.UUCP Reply-To: Rahul Dhesi Lines: 23 In <1991May10.155454.2239@maths.nott.ac.uk> anw@maths.nott.ac.uk (Dr A. N. Walker) writes: >Suppose you write a [purported] halting problem solver. I'll >assume it's in C, so you have a program source called, say, "fred.c", >which compiles into a binary program "fred", running under Unix. The >idea is that you call > $ fred jim.c Suppose jim.c halts when given certain inputs and does not halt when given certain other inputs. The halting problem in this case has not been correctly defined, since the command line "fred jim.c" does not specify the inputs given to jim.c. We we really ought to be saying % fred jim.c fred.c where jim.c is the program whose halting characteristics are being tested, and fred.c is the input that jim.c will be assumed to read when it executes. -- Rahul Dhesi UUCP: oliveb!cirrusl!dhesi