[R] Parsing regular expressions differently - feature request

John Wiedenhoeft john at nurfuerspam.de
Sat Nov 8 13:20:32 CET 2008

Hi there,

I rejoiced when I realized that you can use Perl regex from within R. However, 
as the FAQ states "Some functions, particularly those involving regular 
expression matching, themselves use metacharacters, which may need to be 
escaped by the backslash mechanism. In those cases you may need a quadruple 
backslash to represent a single literal one. "

I was wondering if that is really necessary for perl=TRUE? wouldn't it be 
possible to parse a string differently in a regex context, e.g. automatically 
insert \\ for each \ , such that you can use the perl syntax directly? For 
example, if you want to input a newline as a character, you would use \n 
anyway. At the moment one says \\n to make it clear to R that you mean \n to 
make clear that you mean newline... this is pretty annoying. How likely is it 
that you want to pass a real newline character to PCRE directly?

If it's anyhow possible to pass everything between " and " directly to PCRE 
without expanding it internally in R, please add this to a future version (as 
an option like noescape=TRUE perhaps?)! I would love to use R instead of Perl 
for working with regex, without having to do two levels of escape all the 


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