I think there is a problem in the regex standardization proposal regarding the begin- and end-of-line assertions (^ and $). It seems that there is no way to customize their behavior via the traits. This is inconsistent with the word boundary assertion, which is implementable in terms of the word character class (\w). The author of a traits class should be able to specify which characters are line separators. A simple fix would be to add a character class for line separator characters. Then, ^ and $ could be implemented in terms of lookup_classname and isctype, just as the word boundary assertion is. This leaves out an important corner case, though: \r is a line separator only if it is not immediately followed by a \n. I haven't yet come up with a traits interface that clean enough and general enough to satisfy. I'm open to suggestions. -- Eric Niebler Boost Consulting www.boost-consulting.com