    <p>
        For those Target/Source combinations which don't require range checking,
        this is an empty inline function.
      </p>
      <p>
        If the user supplied a <a class="link" href="numeric_converter_policy_classes.html#boost_numericconversion.numeric_converter_policy_classes.policy_userrangechecker" title="Policy UserRangeChecker">UserRangeChecker</a>
        policy, is this policy which implements this function, so the implementation
        is user defined, although it is expected 