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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]] ?

>
> 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
>
> --
> *******************
> 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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