[Boost-users] [Range] Single Pass Range functionality

In the Boost Range documentation describing the Range concepts for a single pass range it lists in the expression semantics post-condition for boost::begin(a): "boost::begin(a) is either dereferenceable or past-the-end. It is past-the-end if and only if boost::distance(a) == 0." However the documentation for single pass range does not list boost::distance as a valid expression nor in the reference section is boost::distance listed as a single pass range function. Is boost::distance a valid function when applied to a single pass range ?