Re: ! operator
- To: mathgroup at smc.vnet.net
- Subject: [mg55934] Re: [mg55927] ! operator
- From: DrBob <drbob at bigfoot.com>
- Date: Sun, 10 Apr 2005 23:07:11 -0400 (EDT)
- References: <200504101055.GAA29078@smc.vnet.net>
- Reply-to: drbob at bigfoot.com
- Sender: owner-wri-mathgroup at wolfram.com
This bug is particularly odd, since Trace gives exactly the same results both ways:
!MemberQ[{1,2,3},3]//Trace
{{MemberQ[{1,2,3},3],True},!True,False}
Not@MemberQ[{1,2,3},3]//Trace
{{MemberQ[{1,2,3},3],True},!True,False}
The second statement (without Trace) outputs False, but the first yields nothing.
Bobby
On Sun, 10 Apr 2005 06:55:02 -0400 (EDT), DongGook Park <dgpark6 at sunchon.ac.kr> 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
>
>
>
>
>
--
DrBob at bigfoot.com
- References:
- ! operator
- From: "DongGook Park" <dgpark6@sunchon.ac.kr>
- ! operator