If you want all the matches (including overlaps) then you could try one
of these:
> gregexpr("(?=abab)","ababab",perl=TRUE)
[[1]]
[1] 1 3
attr(,"match.length")
[1] 0 0
> gregexpr("ab(?=ab)","ababab",perl=TRUE)
[[1]]
[1] 1 3
attr(,"match.length")
[1] 2 2
The book "Mastering Regular Expressions" by Jeffrey Friedl has a lot of
detail on the hows and whys of regular expression matching.
--
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
[EMAIL PROTECTED]
(801) 408-8111
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED] On Behalf Of
> [EMAIL PROTECTED]
> Sent: Wednesday, October 10, 2007 8:36 AM
> To: [EMAIL PROTECTED]
> Cc: [EMAIL PROTECTED]
> Subject: [Rd] gregexpr (PR#9965)
>
> Full_Name: Peter Dolan
> Version: 2.5.1
> OS: Windows
> Submission from: (NULL) (128.193.227.43)
>
>
> gregexpr does not find all matching substrings if the
> substrings overlap:
>
> > gregexpr("abab","ababab")
> [[1]]
> [1] 1
> attr(,"match.length")
> [1] 4
>
> It does work correctly in Version 2.3.1 under linux.
>
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