I'm having a problem using real_parser, I define the parser as: real_parser<some-type> const rr_p; Then use it as: str_p("range")[assign_a(started, false)] && rr_p[assign_a(a)] && rr_p[assign_a(b)] Followed by a list of other alternative commands. When some-type is float/double/long double it all works OK, but as soon as I change some-type to boost::math::ntl::RR then I have two problems: 1) The code doesn't compile: spirit looks for std::pow rather than relying on ADL to find the right overload, I can work around this one for now by importing boost::math::ntl::pow into namespace std. 2) The parser doesn't work, any simple command like "range 0 1" is rejected as invalid. Is there something else I need to do here to enable support for UDT's? Thanks, John.