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Re: List of position-specifying functions

  • To: mathgroup at smc.vnet.net
  • Subject: [mg102369] Re: [mg102351] List of position-specifying functions
  • From: Leonid Shifrin <lshifr at gmail.com>
  • Date: Fri, 7 Aug 2009 05:29:13 -0400 (EDT)
  • References: <200908061032.GAA01790@smc.vnet.net>

Hi Ray,

here is one way:

In[1]:= plist = {2, 5, 4, 6, 3};


In[2] := Map[Function[x, #[[x]] &], plist]

Out[2] = {#1[[2]]&,#1[[5]]&,#1[[4]]&,#1[[6]]&,#1[[3]]&}


Regards,
Leonid



On Thu, Aug 6, 2009 at 2:32 PM, Ray Koopman <koopman at sfu.ca> wrote:

> I have a list of distinct positive integers, such as
>
> In[1]:= plist = {2, 5, 4, 6, 3};
>
> I want to convert it to a list of position-specifying functions,
> such as might be used as the second argument in SplitBy or GatherBy.
> One way that works is:
>
> In[2]:= plist /. p_Integer->(#[[p]]&)
>
> Out[2]= { #1[[2]]&, #1[[5]]&, #1[[4]]&, #1[[6]]&, #1[[3]]& }
>
> I've been trying to get the same thing using Map,
> but I haven't been able to do it. Any suggestions?
>
>



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