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Getting rid of annoying zeroes in algebraic expressions


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.


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