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Re: Regular Expressions [message #24188 is a reply to message #15713]

Thu, 15 March 2001 16:09

John-David T. Smith is currently offline

John-David T. Smith
Messages: 384
Registered: January 2000

Senior Member

Wayne Landsman wrote:
>
> The following is probably a simple question for anyone familiar with
> regular expressions, but I am still trying to learn the STREGEX
> function.
>
> Suppose I want to find the first occurence in a string of an 'l' ithat
> is not part of a double 'l'. For
> example, in the string
>
> IDL> st = 'The rolling hills and lake'
>
> I want to return the character position of the 'l' in lake (=21).
>
> The following expression almost works -- it will search for any 'l'
> which is both preceded and followed by anything that is not "l"
>
> IDL> print,stregex(st, '[^l]l[^l]' )
>
> but it won't work for the string 'The rolling hills and pool' because
> the final 'l' has no characters following it. Any suggestions?

IDL> print, stregex(st,'(^|[^l])l($|[^l])')

which means "a character that is not 'l', or the beginning of the
string, followed by an 'l', followed by a character that is not 'l', or
the end of the string". Aren't you glad Ken Thompson didn't decide
originally to develop regexps in english?

This will also work on

IDL> st = "let's all go the the movies"

JD

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[Message index]

		regular expressions By: Michael Werger on Fri, 04 June 1999 00:00
		Re: Regular expressions By: Brian Jackel on Fri, 10 November 2000 00:00
		Re: Regular expressions By: Martin Schultz on Fri, 10 November 2000 00:00
		Re: Regular expressions By: Liam E. Gumley on Fri, 10 November 2000 00:00
		Re: Regular Expressions By: John-David T. Smith on Thu, 15 March 2001 16:09
		Re: Regular Expressions By: Wayne Landsman on Thu, 15 March 2001 19:24
		Re: Regular Expressions By: John-David T. Smith on Fri, 16 March 2001 09:20
		Re: Regular Expressions By: Pavel A. Romashkin on Mon, 19 March 2001 13:52
		Re: Regular Expressions By: Craig Markwardt on Tue, 20 March 2001 15:23
		Re: Regular Expressions By: John-David T. Smith on Tue, 20 March 2001 15:28
		Re: Regular Expressions By: Mark Hadfield on Tue, 20 March 2001 14:48
		Re: Regular Expressions By: Wayne Landsman on Tue, 20 March 2001 12:14
		Re: Regular Expressions By: Martin Schultz on Tue, 20 March 2001 04:39

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