Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!feeder.erje.net!1.eu.feeder.erje.net!news.swapon.de!eternal-september.org!feeder.eternal-september.org!mx02.eternal-september.org!.POSTED!not-for-mail From: Keith Thompson Newsgroups: comp.lang.c Subject: Re: SAFEcode Date: Sun, 19 Apr 2015 07:32:05 -0700 Organization: None to speak of Lines: 28 Message-ID: <87pp70p4t6.fsf@kst-u.example.com> References: <1f1874ce-edfe-4923-8d66-9bff31b56f0d@googlegroups.com> <87h9shrxzq.fsf@kst-u.example.com> <79e51590-587b-4fc3-8d7d-8c942be64d1b@googlegroups.com> <87iocw9itn.fsf@bsb.me.uk> <58fa4013-d529-4a33-9efb-84e73bf90169@googlegroups.com> <87bnin93sm.fsf@bsb.me.uk> <514d1b8f-b51e-407c-bba7-3da7f9dc8e5e@googlegroups.com> <25777086-a693-4f9f-915d-e40270b64ab3@googlegroups.com> <37d076d8-7e30-43b4-b1fa-e01a5c43a7dd@googlegroups.com> <87d232cz2n.fsf@bsb.me.uk> <90fe17bc-41e0-4263-b347-1c1ec97b3aa4@googlegroups.com> <6afa8b15-6dec-4c68-9ec5-ffdce4b45ff6@googlegroups.com> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: mx02.eternal-september.org; posting-host="9be37d943435275679235b07c7947eef"; logging-data="728"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18I0Zj7Njjn2tx+1ttt929H" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) Cancel-Lock: sha1:EgaIf+bmHEUUVAdmvCYQ1fPiDYc= sha1:vlKICCnc2861eZtwnE5i0H7ei7E= Xref: csiph.com comp.lang.c:60409 Malcolm McLean writes: [...] > You've been told that the input is human-composed English language text > messages. > That's the crucial bit of information you've haven't taken on board. > It also makes a mathematical proof that there is no optimal answer > very difficult, because you can't define what we know about human- > composed English language messages in a rigorous way, but nor is > it sensible to say we know nothing about them. > > An experimentally devised optimal answer isn't difficult, however, > and that might lead you into realising that in fact there's quite > a bit we can say about human-composed text messages. > For example, will the probability density function be a maximum > at infinity, or will it tend to zero at infinity? What about zero? An experimentally devised optimal answer is impossible, because constructing an experiment based on your stated requirements is impossible unless we add more requirements that you haven't stated. Given any allegedly optimal solution, I can construct an experiment consistent with your requiremnts that breaks it. -- Keith Thompson (The_Other_Keith) kst-u@mib.org Working, but not speaking, for JetHead Development, Inc. "We must do something. This is something. Therefore, we must do this." -- Antony Jay and Jonathan Lynn, "Yes Minister"