Re: Abs and Sign anomolies

*To*: mathgroup at smc.vnet.net*Subject*: [mg7411] Re: Abs and Sign anomolies*From*: hans.steffani at e-technik.tu-chemnitz.de (Hans Steffani)*Date*: Sat, 31 May 1997 15:07:19 -0400 (EDT)*Organization*: University of Technology Chemnitz, FRG*Sender*: owner-wri-mathgroup at wolfram.com

Jack Goldberg <jackgold at math.lsa.umich.edu> writes: >In[1] Abs[Sign[x]] >Out[1] 1 My system delivers: In[1] Abs[Sign[x]] // Simplify Out[1] Abs[Sign[x]] and In[2] Abs[Sign[0]] Out[2] 1 h.f.s. >which is wrong if x = 0. For, Sign[0] = 0 and Abs[0] = 0. So that the >output of Abs[Sign[x]] should be unsimplified. Indeed, Mma returns > Abs[Sign[0]] = 0 >Although multiple crashes (hard and soft) and exporting graphics are >extremely annoying, a mathematical "bug" is a far more serious problem. >A programming error like this can lead to disaster and I urge the >newsgroup to post all such anomalies as soon as they are discovered. We >cannot assume that contacting Wolfram Research will result in a warning >in their FAQ site, nor a timely fix. >Wouldn't it be nice if someone (other than Wolfram Research)) could keep >track of all mathematical "bugs" much the way one of our people keep >track of relative speeds of the kernel on different platforms? The >advantages for all of us are so clear that no argument need be given. >I would be willing to do this, but - I'm embarrasses to admit - I don't >know how to set up a Web page or whatever so that people could access >the complilations automatically! If anyone wishes to send me their >discoveries I will be happy to confirm them and keep a list. >Jack Goldberg >University of Michigan >Ann Arbor Michigan >e-mail: jackgold at math.lsa.umich.edu -- Hans Friedrich Steffani Institut fuer Elektrische Maschinen und Antriebe, TU Chemnitz-Zwickau mailto:hans.steffani at e-technik.tu-chemnitz.de http://www.tu-chemnitz.de/~hfst/