I'd like to shed some light on a couple of points. The stuff I offer is dedicated to two tasks: * building an ANFA (that's Augmented NFA) from an expression tree of a given regex; * running the result against a given input string. What such a code desperately needs, is the following: * syntactical front-end: a class that would parse the actual regex string and build its expression tree; * character back-end: a class that would allow checking whether a given character is contained in a given character set, respecting encodings, locales etc. Boost.regex employs quite a general approach to these components. Reusing them and connecting my code to them is what I have in mind. The only snag is, I'm not familiar with boost.regex internals. So, any help in that field would be appreciated. -- Best regards, Vladimir Pozdyayev.