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MathGroup Archive 1991

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PolynomialQ

  • To: mathgroup at yoda.ncsa.uiuc.edu
  • Subject: PolynomialQ
  • From: Markus Lautenbacher <lauten at srv.cip.Physik.TU-Muenchen.DE>
  • Date: Fri, 11 Jan 91 19:46:51 +0100

In response to jack at chopin.udel.edu (Jack Seltzer)'s "PolynomialQ"
question bc at uxa.cso.uiuc.edu (Ben Cox) writes:

> No, this is correct.  PolynomialQ[expr,{x}] fails only if expr uses x in
> such a way that would forbid it (e.g., Log[x]).
> This is mathematically correct: 0 is a polynomial in x, for example.

,but then what about the following example form the MATHEMATICA book 
(page 383):

>> Mathematica (sun4) 1.2 (June 13, 1990) [With pre-loaded data]
>> by S. Wolfram, D. Grayson, R. Maeder, H. Cejtin,
>>    S. Omohundro, D. Ballman and J. Keiper
>> with I. Rivin and D. Withoff
>> Copyright 1988,1989,1990 Wolfram Research Inc.
>>  -- X11 windows graphics initialized -- 
>> 
>> In[1]:= t = Expand[ (1+x)^3 (1-y-x)^2 ]
>>                    2      3    4    5                    3        4      2
>> Out[1]= 1 + x - 2 x  - 2 x  + x  + x  - 2 y - 4 x y + 4 x  y + 2 x  y + y 
>>
>>           2      2  2    3  2
>> >  + 3 x y  + 3 x  y  + x  y
>> 
>> In[2]:= PolynomialQ[t,x]
>> 
>> Out[2]= True

while the book states that this should give "Out[3]= False" !. 

So the "bug claim" doesn't seem to be wiped off.

MARKUS

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