[Rd] gregexpr - match overlap mishandled (PR#13391)

From: <rthompso_at_aecom.yu.edu>
Date: Fri, 12 Dec 2008 18:05:04 +0100 (CET)

Full_Name: Reid Thompson
Version: 2.8.0 RC (2008-10-12 r46696)
OS: darwin9.5.0
Submission from: (NULL) (

the gregexpr() function does NOT return a complete list of global matches as it should. this occurs when a pattern matches two overlapping portions of a string, only the first match is returned.

the following function call demonstrates this error (although this is not how I initially discovered the problem):
gregexpr("11221122", paste(rep("1122", 10), collapse=""))

instead of returning 9 matches as one would expect, only 5 matches are returned . . .

[1] 1 9 17 25 33

[1] 8 8 8 8 8

you will note, essentially, that the entire first match is then excluded from subsequent matching

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