Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!dali.cs.montana.edu!caen!ox.com!math.fu-berlin.de!dww From: dww@math.fu-berlin.de (Debora Weber-Wulff) Newsgroups: comp.theory Subject: Re: Question on halting problem Keywords: for 10 bonus points... Message-ID: Date: 29 Apr 91 17:00:04 GMT References: <1991Apr26.135918.8607@m.cs.uiuc.edu> <1161@creatures.cs.vt.edu> Sender: news@math.fu-berlin.de (Math Department) Organization: Free University of Berlin, Germany Lines: 22 lavinus@csgrad.cs.vt.edu writes: > >My personal favorite is the following: > >proc foo(n) > while (n > 1) > if (even(n)) n = n div 2 > else n = 3 * n + 1 >end > >As far as I know, it has never been proven that this program halts for all >n. Evidence to the contrary would be quite welcome (BTW, I believe the >credit for this problem is due to Ulam). In Germany, we learn that the "Rollercoaster Function" (Achterbahn- funktion) is due to the famous (German!) Mathematician Collatz. -- Debora Weber-Wulff snail: FU Berlin, ZI Fachdidaktiken, Habelschwerdter Allee 45, W-1000 Berlin 33 email: weberwu@inf.fu-berlin.de, dww@math.fu-berlin.de