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MathGroup Archive 2000

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Re: pure functions

  • To: mathgroup at smc.vnet.net
  • Subject: [mg23345] Re: pure functions
  • From: Roland Franzius <Roland.Franzius at uos.de>
  • Date: Thu, 4 May 2000 02:59:13 -0400 (EDT)
  • Organization: RRZN - Newsserver Test
  • References: <8eg4bn$g5i@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

One of \infty ways to accomplish your task is to Apply Plus to the inner
Lists:
Map[Apply[Plus,#]&,{a,b},{c,d}]
{a+b,c+d}

Your 2nd question is not quite clear to me. do you think of something
like
Select[{1, 2, 3, 4, 5, 6}, Function[{x}, x > 3]] ?

 
Helge Andersson wrote:
> 
> Hello,
> 
> Of all the nice functions such as Map, Mapall, Thread, Apply .... I have
> not been able to write a simple code to generate the following
> procedure.
> 
> I have a two dimensional list like
> 
> li={{11,12,13,..},{21,22,23,...},{31,32,33,..},...}
> 
> Since i like to use the pure function command I would like to map my
> pure function with arguments #1,#2,#3,.... on all the sublists in li.
> 
> Let me exemplify with a simple pure function that add to numbers.
> (#1+#2)&
> 
> if exli={{1,2},{3,4},{5,6},{7,8}}
> 
> then I want to get the result
> {3,7,11,15}
> 
> One solution, but not allways suitable for me, is the following
> 
> (#1+#2)&[Sequence @@ Transpose[exli]].
> 
> I want to get rid of the Transpose command and if possible also making
> use of the /@ notation for Map. Since I have seen so many elegant
> examples in the mailing lists I hope  I can get something out of this.
> 
> Finally, When using pure functions inside Mathematica defined functions
> such as Select for instance,
> Select[{1,2,3,4,5,6},#>3&]
> why don't we need to specify the argument list after the &sign. I can
> figure out that in this case the list sent to the Select command will be
> used as argument list for the pure function but how does this work in
> general. Which are the functions where this feature is possible?
> 
> /Helge
> 
> --
> *******************
> Helge Andersson
> Oorganisk miljökemi
> CTH
> 412 96 Göteborg
> 
> Tel. 031-772 8072
> Tel. Lab. 031-55 38 67
> Fax  031-772 28 53

-- 
Roland Franzius
Theor. Physik FB Physik, Univ. Osnabrueck

  +++ exactly <<n>> lines of this message have value <<FALSE>> +++


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