Re: ! operator

*To*: mathgroup at smc.vnet.net*Subject*: [mg55965] Re: [mg55927] ! operator*From*: János <janos.lobb at yale.edu>*Date*: Tue, 12 Apr 2005 05:26:18 -0400 (EDT)*References*: <200504101055.GAA29078@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

On my machine: In[7]:= Not[MemberQ[{1,2,3},3]] Out[7]= False So it is just he shortcut of ! in place of Not[] which does not work. In[13]:= $Version Out[13]= "5.1 for Mac OS X (October \ 25, 2004)" János On Apr 10, 2005, at 6:55 AM, DongGook Park wrote: > > Hi, > > Could you explain a mysterious behaviour of "! operator" as shown > below? > > > In[43]:= > MemberQ[{1,2,3},3] > > Out[43]= > True > > In[47]:= > !MemberQ[{1,2,3},3] > (* Here Mathematica does not give any response! *) > > In[48]:= > Not@MemberQ[{1,2,3},3] > > Out[48]= > False > > > Considering the description from Mathematica help: > "!expr is the logical NOT function. It gives False if expr is > True, > and True if it is False." > This behaviour seems quite suspicious? > > > DongGook > > > ---------------------------------- > DongGook Park, > School of Information Technology, > SunChon University, Korea > Telephone: +82 61 750 3597 > Mobile: +82 18 732 2125 > Home page: http://www.dgpark6.com/ > Email: dgpark6 at sunchon.ac.kr > ---------------------------------------------- Trying to argue with a politician is like lifting up the head of a corpse. (S. Lem: His Master Voice)

**References**:**! operator***From:*"DongGook Park" <dgpark6@sunchon.ac.kr>