[boost] [smart_ptr] No implicit conversion of shared_array

Hi why doesn't shared_array allow the same conversions as shared_ptr, so that boost::shared_ptr<int> ip; boost::shared_ptr<const int> ip2(ip); is allowed, but not boost::shared_array<int> ip; boost::shared_array<const int> ip2(ip); Is it safe to use shared_ptr's with arrays if one supplies an array deleter as a constructor argument? Thanks in advance for any hint. Regards, Stephan