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MathGroup Archive 2005

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Re: position of a pattern in a list

  • To: mathgroup at smc.vnet.net
  • Subject: [mg58142] Re: [mg58138] position of a pattern in a list
  • From: Andrzej Kozlowski <andrzej at akikoz.net>
  • Date: Mon, 20 Jun 2005 05:21:18 -0400 (EDT)
  • References: <200506190744.DAA05737@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

On 19 Jun 2005, at 16:44, mark wrote:

> *This message was transferred with a trial version of CommuniGate 
> (tm) Pro*
> hi
> i want to search for the positions
>  of the pattern "b" ~~ "c"
> in the list:
> lst = {{{"abcd", "cv"}, {"z", "zzbcz"}}
> , {{"v"}, {"zbcx"}, {"xc", "bc"}}}
> q = StringCases[#, "b" ~~ "c"] & /@ # & /@ lst
> Out[]={{{{bc}, {}}, {{}, {bc}}}, {{{}}, {{bc}}, {{}, {bc}}}}
> Position[q, {"bc"}]
> Out[]={{1, 1, 1}, {1, 2, 2}, {2, 2, 1}, {2, 3, 2}}
> this is okay.
> but suppose i want to use position directly in the same way
> i have used StringCases:
> Position[#, "b" ~~ "c"] & /@ # & /@ lst
> Out[]={{{}, {}}, {{}, {}, {{2}}}}
> or
> Position[lst, "b" ~~ "c"]
> Out[]={{2, 3, 2}}
> here the Position function could not detect the wanted pattern but  
> only the last explicit "bc", i hope you have ideas about this  
> behaviour.
> my second question: can mathematica color  "{" and "}" of the deep  
> nested list in a suitable way so the reader can pursue which one is  
> related to which. if not i think this is a valuable addition in any  
> future versions of mathematica.
> thanks
>
>

One possible way could be:

DeleteCases[Cases[lst,x_String:>If[StringPosition[x,"bc"] != {},{
       Position[lst,x],StringPosition[x,"bc"]}],Infinity],Null]


{{{{1,1,1}},{{2,3}}},{{{1,2,2}},{{3,4}}},{{{2,2,1}},{{2,3}}},{{{
     2,3,2}},{{1,2}}}}


Andrzej Kozlowski


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