Re: Pure Function within a pure function
- To: mathgroup at smc.vnet.net
- Subject: [mg59306] Re: Pure Function within a pure function
- From: David Bailey <dave at Remove_Thisdbailey.co.uk>
- Date: Fri, 5 Aug 2005 01:21:33 -0400 (EDT)
- References: <dcsbi3$pub$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
ggroup at sarj.ca wrote:
> Hi,
>
> I'm wondering if it is possible to define a pure function within a
> function, and if so, what syntax should I be using?
>
> I have some data that I want to filter, say:
>
> rawdata[[1]]=
> time1 pt1-1 pt1-2 pt1-3
> time2 pt2-1 pt2-2 pt2-3
> time3 aborted!
>
> rawdata[[2]]=
> time1 pta-1 pta-2 pta-3
> time2 aborted!
>
> I have a list of such data sets, and I want to apply a filter to remove
> the "aborted" lines to each set. With a table command, this is fairly
> easy:
>
> data = Table[
> Select[rawdata[[i]],Length[#]==4&],
> {i,Length[rawdata]}
> ]
>
> For readability (and lets face it, for pure asthetic value), I was
> hoping to convert this to a function which I could map onto my rawdata
> array. I tried something like:
>
> data = Select[#, Length[#]==4&]& /@ rawdata;
>
> But this doesn't work. I imagine the confusion is with the comparison
> function Length[#]==4&, but I'm having no luck figuring out how to make
> it less ambiguous.
>
> Any pointers would be much appreciated.
>
> Thanks!
>
> PS: I'm using version 5.2 on Windows.
>
Hello,
There is a real ambiguity here, I think because the symbol # might refer
to an inner argument or an outer one! There is, however, a slightly more
verbose way to define a pure function using Function. In this form, the
arguments are named, so no confusion would arise.
David Bailey
http://www.dbaileyconsultancy.co.uk