Eroare de compilare: user.cpp: In function ‘int main()’: user.cpp:27:17: warning: unused variable ‘z’ [-Wunused-variable] int x,y,z; ^ In file included from /usr/include/c++/4.8/algorithm:62:0, from /usr/include/i386-linux-gnu/c++/4.8/bits/stdc++.h:64, from user.cpp:1: /usr/include/c++/4.8/bits/stl_algo.h: In instantiation of ‘_RandomAccessIterator std::__unguarded_partition(_RandomAccessIterator, _RandomAccessIterator, const _Tp&) [with _RandomAccessIterator = gagica*; _Tp = gagica]’: /usr/include/c++/4.8/bits/stl_algo.h:2307:70: required from ‘_RandomAccessIterator std::__unguarded_partition_pivot(_RandomAccessIterator, _RandomAccessIterator) [with _RandomAccessIterator = gagica*]’ /usr/include/c++/4.8/bits/stl_algo.h:2338:54: required from ‘void std::__introsort_loop(_RandomAccessIterator, _RandomAccessIterator, _Size) [with _RandomAccessIterator = gagica*; _Size = int]’ /usr/include/c++/4.8/bits/stl_algo.h:5475:36: required from ‘void std::sort(_RAIter, _RAIter) [with _RAIter = gagica*]’ user.cpp:32:22: required from here /usr/include/c++/4.8/bits/stl_algo.h:2266:20: error: no match for ‘operator<’ (operand types are ‘gagica’ and ‘const gagica’) while (*__first < __pivot) ^ /usr/include/c++/4.8/bits/stl_algo.h:2266:20: note: candidates are: user.cpp:8:10: note: bool gagica::operator<(gagica&) bool operator< ( gagica& ref ){ ^ user.cpp:8:10: note: no known conversion for argument 1 from ‘const gagica’ to ‘gagica&’ In file included from /usr/include/c++/4.8/regex:62:0, from /usr/include/i386-linux-gnu/c++/4.8/bits/stdc++.h:108, from user.cpp:1: /usr/include/c++/4.8/bits/regex.h:1334:5: note: template<class _Bi_iter> bool std::operator<(const std::sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&) operator<(const sub_match<_Bi_iter>& __lhs, ^ /usr/include/c++/4.8/bits/regex.h:1334:5: note: template argument deduction/substitution failed: In file included from /usr/include/c++/4.8/algorithm:62:0, from /usr/include/i386-linux-gnu/c++/4.8/bits/stdc++.h:64, from user.cpp:1: /usr/include/c++/4.8/bits/stl_algo.h:2266:20: note: ‘gagica’ is not derived from ‘const std::sub_match<_BiIter>’ while (*__first < __pivot) ^ In file included from /usr/include/c++/4.8/regex:62:0, from /usr/include/i386-linux-gnu/c++/4.8/bits/stdc++.h:108, from user.cpp:1: /usr/include/c++/4.8/bits/regex.h:1254:5: note: template<class _Bi_iter> bool std::operator<(const typename std::iterator_traits<_Iter>::value_type&, const std::sub_match<_BiIter>&) operator<(typename iterator_traits<_Bi_iter>::value_type const& __lhs, ^ /usr/include/c++/4.8/bits/regex.h:1254:5: note: template argument deduction/substitution failed: In file included from /usr/include/c++/4.8/algorithm:62:0, from /usr/include/i386-linux-gnu/c++/4.8/bits/stdc++.h:64, from user.cpp:1: /usr/include/c++/4.8/bits/stl_algo.h:2266:20: note: ‘const gagica’ is not derived from ‘const std::sub_match<_BiIter>’ while (*__first < __pivot) ^ In file included from /usr/include/c++/4.8/regex:62:0, from /usr/include/i386-linux-gnu/c++/4.8/bits/stdc++.h:108, from user.cpp:1: /usr/include/c++/4.8/bits/regex.h:1177:5: note: template<class _Bi_iter> bool std::operator<(const std::sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)