C++ boost shared_ptr as a hash_map key

http://www.cppblog.com/Solstice/archive/2013/01/28/197597.html

http://stackoverflow.com/questions/6404765/c-shared-ptr-as-unordered-sets-key

http://stackoverflow.com/questions/900369/c-boost-shared-ptr-as-a-hash-map-key

http://stackoverflow.com/questions/8771440/stdset-and-boostshared-ptr-unique-key-identification-issues

http://stackoverflow.com/questions/4145957/can-you-use-a-boostshared-ptr-as-a-key-for-a-map

http://stackoverflow.com/questions/13988735/unordered-map-of-shared-ptrs-breaks-c-program