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Re: Re: Re: Bug Report - Two numerical values for a same variable
*To*: mathgroup at smc.vnet.net
*Subject*: [mg54352] Re: [mg54300] Re: [mg54271] Re: Bug Report - Two numerical values for a same variable
*From*: Andrzej Kozlowski <akoz at mimuw.edu.pl>
*Date*: Sat, 19 Feb 2005 02:31:53 -0500 (EST)
*References*: <00ed01c512b0$2f242850$6400a8c0@Main> <curpbn$r28$1@smc.vnet.net> <200502150438.XAA29728@smc.vnet.net> <200502161936.OAA19223@smc.vnet.net> <d3d3aacf7f18939828890ce85676bd26@mimuw.edu.pl> <opsmcn3rqciz9bcq@monster>
*Sender*: owner-wri-mathgroup at wolfram.com
It has occured to me that it may be a good idea to summarize what (in
my opinion) is the situation concering this issue of Complex, Rational,
Atoms etc.
The following are the two basic Matheamtica principles.
1. All numbers, that is all expressions for which NumberQ returns True
are atoms:
In[1]:=
NumberQ[2/3]
AtomQ[2/3]
AtomQ[2/3]
NumberQ[I]
NumberQ[2+I]
AtomQ[2+I]
Out[1]=
True
Out[2]=
True
Out[3]=
True
Out[4]=
True
Out[5]=
True
Out[6]=
True
2. Numeric quantities that are not numbers (NumberQ returns False) are
Atoms only if they have Head Symbol:
In[7]:=
NumberQ[Pi+I]
AtomQ[Pi+I]
Out[7]=
False
Out[8]=
False
However
In[9]:=
NumberQ[Pi]
Out[9]=
False
In[10]:=
AtomQ[Pi]
Out[10]=
True
In[11]:=
Head[Pi]
Out[11]=
Symbol
Expressions of the form Complex[a,b], Rational[a,b] are only defined
where a and b are (certain) numbers. In particular they are not defined
for numeric quantities whcih are not numbers, e.g. Complex[Pi,E] and
Rational[Pi,Pi] are just undefined expressions.
Andrzej Kozlowski
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