[R] Parsing regular expressions differently - feature request

From: John Wiedenhoeft <john_at_nurfuerspam.de>
Date: Sat, 08 Nov 2008 13:20:32 +0100


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 time.

Thanks,
John



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