[R] gsubfn, strapply, REGEX Problem

[Gabor Grothendieck]

The default has changed to be the negative of its prior
value so that would account for it.  The current
default is backref = -k where k is the number of left parens in
the regexp.  That means that it passes only the
back references (and not the match) if it thinks there
are any backreferences.  Usually this revised default
is what is wanted but the unusual aspect of this example
is that the parens don't represent back references
and the "wrong" default happened to work anyways.

I guess the bottom line is that if you use parens in
your regexp that are not intended to be back references
then its important to specify backref= explicitly.

The NEWS file in the gsubfn distribution does mention
the change.

On Tue, Oct 28, 2008 at 8:32 AM, Johannes Graumann
<johannes_graumann at web.de> wrote:
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> Thanks for looking at this. The "\"" was an oversight for the example, but the "backref" bit solves my problem ... I wonder whether that used to be the default and was recently changed?
>
> Thanks for your help!
>
> Joh
>
> Gabor Grothendieck wrote:
>
>> There is no quote terminating the first argument and you
>> need to add the backref = 0 argument so that it does
>> not interpret the parentheses in the regular expression
>> as back references.
>>
>> Its not clear to me what the intention is here so there
>> may be further changes needed but the ones above
>> result in no error message.
>>
>> On Tue, Oct 28, 2008 at 7:39 AM, Johannes Graumann
>> <johannes_graumann at web.de> wrote:
>>> Hi all,
>>>
>>> I swear this used to work:
>>>
>>> library(gsubfn)
>>> strapply("S(AC,P)TVDK(8)EELVQK(8), ".[(].{1,2}[)]|.")[[1]]
>>>
>>> But somewhere along the update path it stopped ... now giving me this
>>>
>>> Error in base::gsub(pattern, rs, x, ...) :
>>>  invalid backreference 2 in regular expression
>>>
>>> Can't figure it out. What am I doing wrong?
>>>
>>> Thanks for any hints, Joh
>>>
>>> ______________________________________________
>>> R-help at r-project.org mailing list
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>>> PLEASE do read the posting guide
>>> http://www.R-project.org/posting-guide.html and provide commented,
>>> minimal, self-contained, reproducible code.
>>>
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html and provide commented,
>> minimal, self-contained, reproducible code.
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> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>