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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

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