[boost] [pool] boost::details::pool::lcm parameters

Quick question: In boost/pool/detail/gcd_lcm.hpp, why does template <typename Integer> Integer lcm(const Integer & A, const Integer & B); take its parameters as const references instead of just passing the values? I don't see a reason to do this; gdc(A, B) takes values. Thanks, Daniel P.S. As seen in boost_1_35_0_RC2, aka boost-posix-2008-03-21.