Isn't it possible to use 'Repeats' in the lookaheads for boost:regex?

Answer 1

Just based on POSIX I'd say your regex is "DEL_TYPE_([ND]ONE|WAIT),"

That's just based on what you've listed above. I would say that the actual issue is with you double escaping the t; you should probably do [ \t\s]* since there may not be just zero or one tab/space.

Answer 2

I found the answer. No from this manual

Lookbehind

(?<=pattern) consumes zero characters, only if pattern could be matched against the characters preceding the current position (pattern must be of fixed length).