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Re: stregex question [message #67463 is a reply to message #67221]

Tue, 21 July 2009 17:19

JDS
Messages: 94
Registered: March 2009

Member

On Jul 21, 12:53 pm, mgalloy <mgal...@gmail.com> wrote:
> wlandsman wrote:
>> I'd like to find the first "e" in a string that is not next to
>> another "e"
>
>> The solution
>> stregex(s,"e[^e]|$") ;"e" followed by not "e" or at the end of the
>> line
>> doesn't work for the string st = 'see me' because it will find the
>> second "e" in "see"
>
>> The soluton
>> stregex(s,"e{1}") ;Find one occurrence of "e"
>> also finds the first "e" in "see" (Two occurrences is also one
>> occurrence)
>
>> In Perl it seems that one would use the "lookahead" option, but that
>> doesn't seem to be available in stregex().
>
>> (Actually I am looking for the first quote that is not part of a
>> double quote, but I wanted to keep the example syntax simple.)
>> Thanks, --Wayne
>
> I would do something like:
>
> IDL> pos = stregex(s, '([^e]e[^e])|(^e[^e])|(^e$)|([^e]e$)')
> IDL> pos += strmid(s, pos, 1) ne 'e'
>
> You have to add one to pos if either the [^e]e[^e] or [^e]e$ forms matched.

Or, somewhat simpler, and a little easier to maintain:

IDL> pos =(stregex('see me','([^e]|^)(e)([^e]|$)',/SUB))[2]

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[Message index]

		Re: stregex question By: Michael Galloy on Tue, 21 July 2009 09:53
		Re: stregex question By: JDS on Tue, 21 July 2009 17:19
		Re: stregex question By: wlandsman on Tue, 21 July 2009 10:58

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