Re: Multiplication by 0.0

*To*: mathgroup at smc.vnet.net*Subject*: [mg24178] Re: [mg24126] Multiplication by 0.0*From*: Andrzej Kozlowski <andrzej at tuins.ac.jp>*Date*: Wed, 28 Jun 2000 22:50:59 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

on 00.6.28 3:11 PM, Brian Higgins at bghiggins at ucdavis.edu wrote: > Dear Mathgroup, > > Consider the following: > In[49]:=0*a > Out[49]=0 > Now if we replace 0 with 0.0 > In[51]:=0.0*a > Out[51]=0.*a > If we set the precision > In[52]:=SetPrecision[0., 0]*a > Out[52]=0 > > What is the simple explanation for this behavior? > > Brian > > > Sent via Deja.com http://www.deja.com/ > Before you buy. > The last bit is easy: In[1]:= SetPrecision[0., 0] Out[1]= 0 so this is just the same as your first example (0*a). As for why 0.*a returns the input unevaluated, it is helpful to ask onself the question: what should the output be? Since a can take represent value, it would seem that any numerical choice would lead to a contradiction. If the answer were to be 0. that would not be consistent with the fact that: In[3]:= 0.*0 Out[3]= 0 (setting a->0). If on the other hand the answer were 0, it would not be consistent with lots of things, e.g. (setting a->1 In[4]:= 0.*1 Out[4]= 0. So I guess the logical choice is to return the input unevaluated and wait for a value to be assigned to a. The may be other reasons too, but the above seem convincing enough to me. -- Andrzej Kozlowski Toyama International University, JAPAN For Mathematica related links and resources try: <http://www.sstreams.com/Mathematica/>