Mathematica 9 is now available
Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2005
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2005

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Re: ! operator

  • To: mathgroup at smc.vnet.net
  • Subject: [mg55943] Re: [mg55933] Re: [mg55927] ! operator
  • From: DrBob <drbob at bigfoot.com>
  • Date: Mon, 11 Apr 2005 03:14:52 -0400 (EDT)
  • References: <200504110307.XAA06436@smc.vnet.net>
  • Reply-to: drbob at bigfoot.com
  • Sender: owner-wri-mathgroup at wolfram.com

Hmm... what does "text-based front end" mean, and is there another kind? Is the standard notebook interface a text-based front end? What's an example of a non-text-based front end for Mathematica?

Trace suggests !expr is interpreted the same as Not[expr] for SOME expressions, at least:

!PrimeQ[12]//Trace

{{PrimeQ[12],False},!False,True}

But, indeed, if I input:

!True

a DOS window comes up briefly and disappears before I can tell what's up. This is a huge surprise to me.

Type this to see the DOS window more clearly:

!pause

Or better yet,

!cmd

However, if I input

!PrimeQ[12]

there is no fleeting DOS window, and still no Output cell. Is that because cmd is a DOS command, but PrimeQ[12] isn't? Can Mathematica be certain of this? (True isn't a DOS command, after all.)

Does "escape sequence" mean "DOS command"? No, I guess not, since

!dir>dum.txt

doesn't pipe directory contents to a file called "dum.txt". (It doesn't do anything at all, as far as I can tell.) So... what's really going on, I wonder?

Bobby

On Sun, 10 Apr 2005 23:07:10 -0400 (EDT), David Park <djmp at earthlink.net> wrote:

> 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
> 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
>
>
>
>
>
>
>
>



-- 
DrBob at bigfoot.com


  • Prev by Date: Re: Series[] command
  • Next by Date: Re: Re: Recommendations for a programming book?
  • Previous by thread: Re: ! operator
  • Next by thread: Re: ! operator