Re: Getting rid of annoying zeroes in algebraic expressions

*To*: mathgroup at smc.vnet.net*Subject*: [mg15241] Re: [mg15228] Getting rid of annoying zeroes in algebraic expressions*From*: "Carl K.Woll" <carlw at fermi.phys.washington.edu>*Date*: Sun, 27 Dec 1998 03:58:33 -0500*Organization*: Department of Physics*References*: <199812230604.BAA02100@smc.vnet.net.>*Sender*: owner-wri-mathgroup at wolfram.com

Hi Sean, Does Chop do what you want? For example, In[1]:= xx=0. + (a*f)/(0. + f) + (b*f)/(0. + f) + (c*f)/(0. + f) Out[1]= a f b f c f 0. + ------ + ------ + ------ 0. + f 0. + f 0. + f In[2]:= Chop[xx] Out[2]= a + b + c As far as your question on Replace, I don't get the behavior you mention: In[15]:= xx/.Plus[0.,q_]->q Out[15]= a f b f c f ------ + ------ + ------ 0. + f 0. + f 0. + f Your other attempt produced an error message for me. On the other hand, to get the behavior you want, you simply need to use ReplaceRepeated, as in In[16]:= xx//.Plus[0.,q_]->q Out[16]= a + b + c Carl Woll Dept of Physics U of Washington Ross, Sean wrote: > Let xx be the result of some algebraic manipulations which, for some > reason, mathematica thinks the real zeroes ought to be kept and I think > they ought to be dropped. > > xx=0. + (a*f)/(0. + f) + (b*f)/(0. + f) + (c*f)/(0. + f) > > xx/.Plus[0.,q_]->q > > returns > > 0. + (a*f)/(0. + f) + (b*f)/(0. + f) + (c*f)/(0. + f) > > while > > 0. + (a*f)/(0. + f) + (b*f)/(0. + f) + (c*f)/(0. + f)/.Plus[0.,q_->q] > > returns the expected > > a+b+c. > > xx is supposed to be equivalent to the expression, but in this case, it > is not. > I can't write a function to automatically drop zeroes if expressions > behave differently when they are alone on an input line and when they > are set equal to a symbol. Does anyone know how to eliminate this kind > of behavior? I am sure it has something to do with some obscure step > in the "standard evaluation cycle" and that there is probably a long, > convoluted explanation as to why someone would want this behavior, but > I don't and I would appreciate it if someone could tell me how to get > rid of it or circumvent it. > > Thanks, > > Sean Ross > > Please reply to rosss at plk.af.mil as I no longer subscribe to the > mathgroup. >

**References**:**Getting rid of annoying zeroes in algebraic expressions***From:*"Ross, Sean" <rosss@plk.af.mil>