[R] Do grep() and strsplit() use different regex engines?

[Bert Gunter]

Thanks Jeff. That doesn't explain it for me. Could you go through the
algorithm a step at a time to show why it splits at the individual
characters rather than the words, perhaps privately. Feel free to
refuse, as I'm sure you have better things to do.

-- Bert


Bert Gunter

"Data is not information. Information is not knowledge. And knowledge
is certainly not wisdom."
   -- Clifford Stoll


On Sat, Jul 11, 2015 at 8:52 AM, Jeff Newmiller
<jdnewmil at dcn.davis.ca.us> wrote:
> "\\b" is a zero length match. strsplit seems to chop at least one character off the beginning of the string if it sees a match, and then it looks at the shortened string that remains and repeats.
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> On July 11, 2015 7:47:22 AM PDT, Bert Gunter <bgunter.4567 at gmail.com> wrote:
>>I noticed the following:
>>
>>> strsplit("red green","\\b")
>>[[1]]
>>[1] "r" "e" "d" " " "g" "r" "e" "e" "n"
>>
>>> strsplit("red green","\\W")
>>[[1]]
>>[1] "red"   "green"
>>
>>I would have thought that "\\b" should give what "\\W" did. Note that:
>>
>>> grep("\\bred\\b","red green")
>>[1] 1
>>## as expected
>>
>>Does strsplit use a different regex engine than grep()? Or more
>>likely, what am I misunderstanding?
>>
>>Thanks.
>>
>>Bert
>>
>>
>>Bert Gunter
>>
>>"Data is not information. Information is not knowledge. And knowledge
>>is certainly not wisdom."
>>   -- Clifford Stoll
>>
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>