[Date Index]
[Thread Index]
[Author Index]
Re: Funny Limits
*To*: mathgroup at yoda.physics.unc.edu
*Subject*: Re: Funny Limits
*From*: Jack Seltzer <jack at chopin.udel.edu>
*Date*: Mon, 30 Sep 91 10:33:07 -0400
>From stevec at yoda.physics.unc.edu Sat Sep 28 05:53:47 1991
>Received: from yoda.physics.unc.edu by brahms.udel.edu with SMTP
> (5.61+/IDA-1.2.8) id AA13640; Sat, 28 Sep 91 05:53:45 -0400
>Received: by yoda.physics.unc.edu (4.0/TAS/11-16-88)
> id AA09908; Fri, 27 Sep 91 22:39:32 CDT
>Received: by yoda.physics.unc.edu (4.0/TAS/11-16-88)
> id AA09904; Fri, 27 Sep 91 22:39:31 CDT
>Message-Id: <9109280339.AA09904 at yoda.physics.unc.edu>
>Date: Wed, 25 Sep 91 10:49:45 PDT
>From: Steve Trainoff <steve at tweedledee.ucsb.edu>
>To: mathgroup at yoda.physics.unc.edu
>Subject: Funny Limits
>Status: RO
>
>Hello all,
>
>I just got my new copy of MMA 2.0 and have been playing around with it. It appears
>to have some annoying "features." I had hoped that the Limit function would be more
>robust under 2.0. Not so. Here is an example. I always thought that the limit of
>x^n/E^x as x->Infinity was zero or all values of n. MMA apparantly thinks
>otherwise, moreover it appears that MMA 2.0 has less persistance than MMA 1.
>Notice that MMA 1.2 got farther than 2.0 and also gave a warning method that it
>couldn't find the answer when it gave up. MMA 2.0 just quit silently.
>
>...STeve
>
>Example 1:
>------------------------------------------------------------
>Mathematica (NeXT) 1.2 (January 20, 1990) [With pre-loaded data]
>by S. Wolfram, D. Grayson, R. Maeder, H. Cejtin,
> S. Omohundro, D. Ballman and J. Keiper
>with I. Rivin and D. Withoff
>Copyright 1988,1989,1990 Wolfram Research Inc.
>
>In[1]:= Table[Limit[x^n/E^x, x->Infinity], {n, 0, 15}]
>
>
>Limit::nlm: Could not find definite limit.
>
>Limit::nlm: Could not find definite limit.
>
>Limit::nlm: Could not find definite limit.
>
>General::stop: Further output of Limit::nlm
> will be suppressed during this calculation.
>
> 13
> x
>Out[1]= {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, Limit[---, x -> Infinity],
>
> x
> E
>
>
> 14 15
> x x
>> Limit[---, x -> Infinity], Limit[---, x -> Infinity]}
(rest of msg deleted)
The problem above is the order of evaluation...using Release eliminates the
difficulty as shown below...
In[15]:= Table[Release[Limit[x^n/E^x,x->Infinity]],{n,0,30}]
Out[15]= {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> 0, 0, 0, 0, 0, 0, 0, 0, 0}
Prev by Date:
**Finite Function (Follow up)**
Next by Date:
**Re: Finite Functions / hash/ fast dispatch**
Previous by thread:
**Re: Funny Limits**
Next by thread:
**Finite Functions**
| |