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Re: harder parts of list

  • To: mathgroup at smc.vnet.net
  • Subject: [mg15609] Re: [mg15570] harder parts of list
  • From: Robert Pratt <rpratt at math.unc.edu>
  • Date: Thu, 28 Jan 1999 04:23:35 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

trim[ls_]:=Select[ls,#<First[ls]&]

Map[trim[#]&,lst]

Rob Pratt
Department of Mathematics
The University of North Carolina at Chapel Hill CB# 3250, 331 Phillips
Hall
Chapel Hill, NC  27599-3250

rpratt at math.unc.edu

http://www.math.unc.edu/Grads/rpratt/

On Tue, 26 Jan 1999, Arnold Knopfmacher wrote:

> This seems to be a harder list parts problem. Given a list like 
> 
> lst={{4,2,3,1},{3,1,5},{2,4,3}}
> 
> I wish to select the elements in each sublist that are smaller than the
> first 
>   entry in that sublist.
> 		So for the above lst the output should be {{2,3,1},{1},{}}. How can I
> do this  with Select or Cases?
> 
> 
> Using pattern matching this works
> 
> rule1={a_,b___,c_,d___}:>{a,b,d} /;c>a
> 
> 
> (# //. rule1)& /@ lst
> 
> {{4,2,3,1},{3,1},{2}}
> 
> Rest /@ %
> 
> {{2,3,1},{1},{}}
> 
> Thanks
> Arnold Knopfmacher
> Wiws University
> South Africa
> 
> 



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