Eroare de compilare: In file included from /usr/local/include/c++/4.8.0/bits/hashtable.h:35:0, from /usr/local/include/c++/4.8.0/unordered_set:47, from user.cpp:9: /usr/local/include/c++/4.8.0/bits/hashtable_policy.h: In instantiation of ‘struct std::__detail::_Hash_code_base<std::pair<int, int>, std::pair<int, int>, std::__detail::_Identity, std::hash<std::pair<int, int> >, std::__detail::_Mod_range_hashing, std::__detail::_Default_ranged_hash, true>’: /usr/local/include/c++/4.8.0/bits/hashtable_policy.h:1402:10: required from ‘struct std::__detail::_Hashtable_base<std::pair<int, int>, std::pair<int, int>, std::__detail::_Identity, std::equal_to<std::pair<int, int> >, std::hash<std::pair<int, int> >, std::__detail::_Mod_range_hashing, std::__detail::_Default_ranged_hash, std::__detail::_Hashtable_traits<true, true, true> >’ /usr/local/include/c++/4.8.0/bits/hashtable.h:174:11: required from ‘class std::_Hashtable<std::pair<int, int>, std::pair<int, int>, std::allocator<std::pair<int, int> >, std::__detail::_Identity, std::equal_to<std::pair<int, int> >, std::hash<std::pair<int, int> >, std::__detail::_Mod_range_hashing, std::__detail::_Default_ranged_hash, std::__detail::_Prime_rehash_policy, std::__detail::_Hashtable_traits<true, true, true> >’ /usr/local/include/c++/4.8.0/bits/unordered_set.h:96:18: required from ‘class std::unordered_set<std::pair<int, int> >’ user.cpp:21:32: required from here /usr/local/include/c++/4.8.0/bits/hashtable_policy.h:1070:12: error: invalid use of incomplete type ‘struct std::hash<std::pair<int, int> >’ struct _Hash_code_base<_Key, _Value, _ExtractKey, _H1, _H2, ^ In file included from /usr/local/include/c++/4.8.0/bits/basic_string.h:3035:0, from /usr/local/include/c++/4.8.0/string:52, from /usr/local/include/c++/4.8.0/bits/locale_classes.h:40, from /usr/local/include/c++/4.8.0/bits/ios_base.h:41, from /usr/local/include/c++/4.8.0/ios:42, from /usr/local/include/c++/4.8.0/ostream:38, from /usr/local/include/c++/4.8.0/iostream:39, from user.cpp:1: /usr/local/include/c++/4.8.0/bits/functional_hash.h:58:12: error: declaration of ‘struct std::hash<std::pair<int, int> >’ struct hash; ^ In file included from /usr/local/include/c++/4.8.0/bits/hashtable.h:35:0, from /usr/local/include/c++/4.8.0/unordered_set:47, from user.cpp:9: /usr/local/include/c++/4.8.0/bits/hashtable_policy.h:1070:12: error: invalid use of incomplete type ‘struct std::hash<std::pair<int, int> >’ struct _Hash_code_base<_Key, _Value, _ExtractKey, _H1, _H2, ^ In file included from /usr/local/include/c++/4.8.0/bits/basic_string.h:3035:0, from /usr/local/include/c++/4.8.0/string:52, from /usr/local/include/c++/4.8.0/bits/locale_classes.h:40, from /usr/local/include/c++/4.8.0/bits/ios_base.h:41, from /usr/local/include/c++/4.8.0/ios:42, from /usr/local/include/c++/4.8.0/ostream:38, from /usr/local/include/c++/4.8.0/iostream:39, from user.cpp:1: /usr/local/include/c++/4.8.0/bits/functional_hash.h:58:12: error: declaration of ‘struct std::hash<std::pair<int, int> >’ struct hash; ^ In file included from /usr/local/include/c++/4.8.0/bits/hashtable.h:35:0, from /usr/local/include/c++/4.8.0/unordered_set:47, from user.cpp:9: /usr/local/include/c++/4.8.0/bits/hashtable_policy.h:1082:53: error: invalid use of incomplete type ‘struct std::hash<std::pair<int, int> >’ using __ebo_h1 = _Hashtable_ebo_helper<1, _H1>; ^ In file included from /usr/local/include/c++/4.8.0/bits/basic_string.h:3035:0, from /usr/local/include/c++/4.8.0/string:52, from /usr/local/include/c++/4.8.0/bits/locale_classes.h:40, from /usr/local/include/c++/4.8.0/bits/ios_base.h:41, from /usr/local/include/c++/4.8.0/ios:42,