[boost] Why there is no boost::rational for non IntType ?

Why there is no boost::rational for non IntType ? I think there are cases where we require such type of rationals, e.g. ( 2 + 3i) / (5 + 6i). In std::complex, we don't have any such constraint on element type of the complex number. That is, though std::complex<double> is quite natural we can have the construct std::complex<int> as well. Is boost::rational<> strictly modeled on the basis of rational numbers ? Another question, is there any continued fraction library in BOOST ? With Regards, Reetesh Mukul