Re: [boost] [Review] xpressive

From: Eric Niebler (eric_at_[hidden])
Date: 2005-09-18 13:46:51

John Maddock wrote:
> there is one complicated 
> expression that xpressive didn't compile, but which Boost.Regex and PCRE 
> did handle OK.

I've tracked this down. xpressive is rejecting this regex because it is 
invalid according to the TR1 spec. It begins:

   const char* highlight_expression =
   "(^[ \t]*#(?:[^\\\\\\n]|"
   "\\\\[^\\n_[:punct:][:alnum:]]*[\\n[:punct:][:word:]])*)|"
----------------------------------------------^^^^^^^^

The problem is [:word:]. "word" is not a valid char-class-name, 
according to the TR1 spec:

"Expressions of the form [[:class-name:]] are recognized, and are 
sensitive to the locale encapsulated by the traits class. The range of 
values for class-name is determined by the traits class, but at least 
the following names are recognized: alnum, alpha, blank, cntrl, digit, 
graph, lower, print, punct, space, upper, xdigit."

If you change your regex to use "\\w" instead of "[:word:]", xpressive 
compiles it fine.

(xpressive sure could give a better error in this case, though. :-/)

-- 
Eric Niebler
Boost Consulting
www.boost-consulting.com