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Re: Question about DeleteCases to remove list elements based on first character

  • To: mathgroup at smc.vnet.net
  • Subject: [mg124350] Re: Question about DeleteCases to remove list elements based on first character
  • From: David Reiss <dbreiss at gmail.com>
  • Date: Tue, 17 Jan 2012 03:30:24 -0500 (EST)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com
  • References: <jf1362$5hn$1@smc.vnet.net>

DeleteCases requires that you work with a pattern. Thus the following
will work for your first example:

DeleteCases[S, _?(StringTake[#, 1] == ";" &)]

gives

{"abc", "ghi", "pqr;X"}

--David

On Jan 16, 6:54 am, Andrew DeYoung <adeyo... at andrew.cmu.edu> wrote:
> Hi,
>
> I have a list of strings in which some elements begin with the ";"
> character and some do not.  The ";" character indicates a program
> comment, so I wish to drop all elements in the list that begin with
> the ";" character.
>
> As a simplified example, suppose I have the following list S:
>
> S = {"abc", ";def", "ghi", ";jkl", ";  mno", "pqr;X"}
>
> I wish to drop from S all elements that begin with ";".  So, I want to
> obtain:
>
> {"abc", "ghi", "pqr;X"}
>
> Will you please help me know how to do this?  Can this be done with
> DeleteCases?  For example, I tried:
>
> DeleteCases[S, StringTake[#, 1] == ";"&]
>
> and
>
> DeleteCases[S, ";" ~~ __]
>
> but I am wrong:  these do not work.  Can you please help me?
>
> Thanks so much.
>
> Andrew DeYoung
> Carnegie Mellon University




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