Re: ! operator

*To*: mathgroup at smc.vnet.net*Subject*: [mg55933] Re: [mg55927] ! operator*From*: "David Park" <djmp at earthlink.net>*Date*: Sun, 10 Apr 2005 23:07:10 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

DongGook, Read the rest of the Help for Not, at least on Version 5... If you are using Mathematica with a text-based front end, then you cannot use the notation !expr for Not[expr] if it appears at the very beginning of a line. In this case, !expr is interpreted as a shell escape. (Certainly a strange 'feature'!) David Park djmp at earthlink.net http://home.earthlink.net/~djmp/ From: DongGook Park [mailto:dgpark6 at sunchon.ac.kr] To: mathgroup at smc.vnet.net 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

**Follow-Ups**:**Re: Re: ! operator***From:*DrBob <drbob@bigfoot.com>