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Re: Logical Expression

• To: mathgroup at smc.vnet.net
• Subject: [mg73424] Re: [mg73385] Logical Expression
• From: Murray Eisenberg <murray at math.umass.edu>
• Date: Fri, 16 Feb 2007 00:57:38 -0500 (EST)
• Organization: Mathematics & Statistics, Univ. of Mass./Amherst
• References: <200702150956.EAA04579@smc.vnet.net>
• Reply-to: murray at math.umass.edu

Try === (SameQ) and =!= (UnsameQ) instead of == (Equal) and ! (Unequal).

Martin Schoenecker wrote:
> Common sense tells me that the statement that "something is equal to
> zero, and unequal to zero at the same time" is a false statement:
> 
> In[1]:= a == 0 && a != 0
> Out[1]= a\[Equal]0&&a=E2=89=A00
> 
> In[2]:= LogicalExpand[%]
> Out[2]= False
> 
> The same, in my opinion, applies to "something is equal to zero and
> greater than zero at the same time".  Why doesn't Mathematica think so,
> and how to convince it to evaluate the following?
> 
> In[3]:= a == 0 && a > 0
> Out[3]= a\[Equal]0&&a>0
> 
> In[4]:= LogicalExpand[%]
> Out[4]= a\[Equal]0&&a>0
> 
> 
> Thanks in advance,
> Martin
> 

-- 
Murray Eisenberg                     murray at math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower      phone 413 549-1020 (H)
University of Massachusetts                413 545-2859 (W)
710 North Pleasant Street            fax   413 545-1801
Amherst, MA 01003-9305

• References:
  • Logical Expression
    • From: Martin Schoenecker <ms_usenet@gmx.de>