Re: ! operator

*To*: mathgroup at smc.vnet.net*Subject*: [mg55932] Re: ! operator*From*: dh <dh at metrohm.ch>*Date*: Sun, 10 Apr 2005 23:07:08 -0400 (EDT)*References*: <d3b18l$sgd$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

DongGook "!" has two meainings as a prefix operator (and even an additional one as a postfix),namely the Not and the Pipe operator. Now Matematica has to decide what you mean. If "!" is the first character on a new line, Mathematica interpretes "!" as the Pipe character. On the other hand, if you write e.g.: t=!MemeberQ... Mathematica interpretes "!" as the Not operator. Sincerely, Daniel 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 > >