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MathGroup Archive 2001

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Re: List-Operations on Heads other than List

  • To: mathgroup at
  • Subject: [mg29743] Re: List-Operations on Heads other than List
  • From: "Orestis Vantzos" <atelesforos at>
  • Date: Fri, 6 Jul 2001 03:24:38 -0400 (EDT)
  • Organization: National Technical University of Athens, Greece
  • References: <9i068k$h0i$>
  • Sender: owner-wri-mathgroup at

I don't really think there are "dangerous" programming styles. You do have
ofcourse "ineffective" programming styles (such as using a horde of Part
operations and For loops to mimic C in Mathematica) and there are
"error-prone" programming styles (such as naming your favourite variable
I think using Select on general structures(not just _List) is fairly safe;
do keep in mind though, that Select searches in all the levels of your
expression and you might get weird results because of this.

"Detlef Mueller" <dmueller at> wrote in message
news:9i068k$h0i$1 at
> Hello,
> The Help Browser says:
> Select[list, crit] picks out all elements ...
> Now this works fin for other Haeders thal List
> too.
> Select[Expand[P], ! NumberQ[#] &] removes the
> absolute Part of the Poynomial P
> (in my Version).
> Is this a dangerous Way of Programming?
> Greetings
>   Detlef

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