Re: Re: Strange phenomenon

• To: mathgroup at smc.vnet.net
• Subject: [mg32151] Re: [mg32140] Re: Strange phenomenon
• From: Andrzej Kozlowski <andrzej at tuins.ac.jp>
• Date: Sat, 29 Dec 2001 18:00:29 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

```Of course you only have yourself to blame when you use mylist[[0]]
meaning something else, because epr[[0]] (Part[exp,0]) is a perfectly
valid Mathematica command which extracts the Head of the expression epr.
This is exactly the same as if you pressed the accelerator instead of
the clutch in a (manual transmission) car and then complained that the
car did not guess your real intention.

Andrzej Kozlowski
Toyama International University
JAPAN
http://platon.c.u-tokyo.ac.jp/andrzej/

On Saturday, December 29, 2001, at 05:57  PM, Steve Gray wrote:

>
> "Steve Gray" <stevebg at adelphia.net> wrote in message
> news:a0jlqg\$31i\$1 at smc.vnet.net...
>>     I do a calculation involving the product of four 5x5 matrices
> containing
>> a bunch of E^(2PiI/5) type terms, and get an answer containing
>> stuff like the following (I did Copy As > Plain Text)
>>
>> \!\(\(\(\(\(\(+2\)\ zr\^4 - \((\(-1\))\)\^\(3/5\)\ \((1 +
>>               List - \((5 + List)\)\ zr +
>>               7\ zr\^2 + \((\(-6\) + List)\)\ zr\^3 +
>>               zr\^4)\) + \((\(-1\))\)\^\(1/5\)\ \((\(-2\) +
>>               List\ \((1 + zr + 2\ zr\^2)\) -
>>               zr\ \((\(-3\) +
>>                     zr\ \((7 + \((\(-4\) +
>>                                 zr)\)\ zr)\))\))\) +
> \((\(-1\))\)\^\(2/5\)\
>> \
>>
>>     It looks like Mathematica thinks "List" is a variable.
>
>     I just found that this is what happens when you have an error
> in the list relative address, specifically when you do mylist[[0]] by
> mistake.
>     This is not a good method of notification of that error.
>
>
>
>

```

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