Re: Logical Expression

*To*: mathgroup at smc.vnet.net*Subject*: [mg73442] Re: [mg73385] Logical Expression*From*: "Chris Chiasson" <chris at chiasson.name>*Date*: Fri, 16 Feb 2007 01:07:32 -0500 (EST)*References*: <200702150956.EAA04579@smc.vnet.net>

The special characters in your email are garbled, which is possibly due to improper character encoding. Anyway, try playing with Experimental`$SameQTolerance and Experimental`$EqualTolerance , which are described in the help browser, I believe. The inequality functions (< <= > >= ) use the SameQ tolerance, while the equality function ( == ) uses the Equal tolerance. You can use SameQ ( === ) instead of Equal ( == ). On 2/15/07, Martin Schoenecker <ms_usenet at gmx.de> 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 > > -- http://chris.chiasson.name/

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