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. > > > >