R help - Feb 2005 - Sub with and without perl=TRUE

I have a problem doing substitution using sub and perl=TRUE when the
elements of x have fewer characters than the replacement string.  Let me
show you what I mean:
> sub("m","billy","m")
[1] "billy"

But using perl=TRUE, I can only return a result as long as my
x:
> sub("m","billy","m",perl=TRUE)
[1] "b"
> sub("m","billy","ma",perl=TRUE)
[1] "bi"

Etc.

Is this supposed to happen like this? I couldn't see a mention of this
requirement in the help.

I am using R 2.0.1 on windows xp.

Robert




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This was a bug which is already fixed in R-2.0.1 patched.  From the NEWS 
file

     o	gsub(perl=TRUE) returned a string which printed with trailing
 	garbage if there was a match at the beginning whose
 	replacement was shorter.  (PR#7479)

The crucial comment is that it only happened for a match at the beginning, 
and sub() was using the same code.

Pre-compiled versions of R-patched for Windows XP are available on CRAN.


On Mon, 14 Feb 2005, Denham Robert wrote:
> I have a problem doing substitution using sub and perl=TRUE when the
> elements of x have fewer characters than the replacement string.  Let me
> show you what I mean:
>
>> sub("m","billy","m")
> [1] "billy"
>
> But using perl=TRUE, I can only return a result as long as my x:
>> sub("m","billy","m",perl=TRUE)
> [1] "b"
>
>> sub("m","billy","ma",perl=TRUE)
> [1] "bi"
>
> Etc.
>
> Is this supposed to happen like this? I couldn't see a mention of this
> requirement in the help.
>
> I am using R 2.0.1 on windows xp.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595