Eroare de compilare: In file included from /usr/include/c++/6/bits/stl_algobase.h:71:0, from /usr/include/c++/6/algorithm:61, from user.cpp:2: /usr/include/c++/6/bits/predefined_ops.h: In instantiation of ‘constexpr bool __gnu_cxx::__ops::_Iter_less_iter::operator()(_Iterator1, _Iterator2) const [with _Iterator1 = Date*; _Iterator2 = Date*]’: /usr/include/c++/6/bits/stl_algo.h:1844:14: required from ‘void std::__insertion_sort(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = Date*; _Compare = __gnu_cxx::__ops::_Iter_less_iter]’ /usr/include/c++/6/bits/stl_algo.h:1882:25: required from ‘void std::__final_insertion_sort(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = Date*; _Compare = __gnu_cxx::__ops::_Iter_less_iter]’ /usr/include/c++/6/bits/stl_algo.h:1968:31: required from ‘void std::__sort(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = Date*; _Compare = __gnu_cxx::__ops::_Iter_less_iter]’ /usr/include/c++/6/bits/stl_algo.h:4707:18: required from ‘void std::sort(_RAIter, _RAIter) [with _RAIter = Date*]’ user.cpp:60:25: required from here /usr/include/c++/6/bits/predefined_ops.h:43:23: error: no match for ‘operator<’ (operand types are ‘Date’ and ‘Date’) { return *__it1 < *__it2; } ~~~~~~~^~~~~~~~ In file included from /usr/include/c++/6/bits/stl_algobase.h:67:0, from /usr/include/c++/6/algorithm:61, from user.cpp:2: /usr/include/c++/6/bits/stl_iterator.h:885:5: note: candidate: template<class _IteratorL, class _IteratorR, class _Container> bool __gnu_cxx::operator<(const __gnu_cxx::__normal_iterator<_IteratorL, _Container>&, const __gnu_cxx::__normal_iterator<_IteratorR, _Container>&) operator<(const __normal_iterator<_IteratorL, _Container>& __lhs, ^~~~~~~~ /usr/include/c++/6/bits/stl_iterator.h:885:5: note: template argument deduction/substitution failed: In file included from /usr/include/c++/6/bits/stl_algobase.h:71:0, from /usr/include/c++/6/algorithm:61, from user.cpp:2: /usr/include/c++/6/bits/predefined_ops.h:43:23: note: ‘Date’ is not derived from ‘const __gnu_cxx::__normal_iterator<_IteratorL, _Container>’ { return *__it1 < *__it2; } ~~~~~~~^~~~~~~~ In file included from /usr/include/c++/6/bits/stl_algobase.h:67:0, from /usr/include/c++/6/algorithm:61, from user.cpp:2: /usr/include/c++/6/bits/stl_iterator.h:892:5: note: candidate: template<class _Iterator, class _Container> bool __gnu_cxx::operator<(const __gnu_cxx::__normal_iterator<_Iterator, _Container>&, const __gnu_cxx::__normal_iterator<_Iterator, _Container>&) operator<(const __normal_iterator<_Iterator, _Container>& __lhs, ^~~~~~~~ /usr/include/c++/6/bits/stl_iterator.h:892:5: note: template argument deduction/substitution failed: In file included from /usr/include/c++/6/bits/stl_algobase.h:71:0, from /usr/include/c++/6/algorithm:61, from user.cpp:2: /usr/include/c++/6/bits/predefined_ops.h:43:23: note: ‘Date’ is not derived from ‘const __gnu_cxx::__normal_iterator<_Iterator, _Container>’ { return *__it1 < *__it2; } ~~~~~~~^~~~~~~~ /usr/include/c++/6/bits/predefined_ops.h: In instantiation of ‘bool __gnu_cxx::__ops::_Iter_less_val::operator()(_Iterator, _Value&) const [with _Iterator = Date*; _Value = Date]’: /usr/include/c++/6/bits/stl_heap.h:129:48: required from ‘void std::__push_heap(_RandomAccessIterator, _Distance, _Distance, _Tp, _Compare) [with _RandomAccessIterator = Date*; _Distance = int; _Tp = Date; _Compare = __gnu_cxx::__ops::_Iter_less_val]’ /usr/include/c++/6/bits/stl_heap.h:230:23: required from ‘void std::__adjust_heap(_RandomAccessIterator, _Distance, _Distance, _Tp, _Compare) [with _RandomAccessIterator = Date*; _Distance = int; _Tp = Date; _Compare = __gnu_cxx::__ops::_Iter_less_iter]’ /usr/include/c++/6/bits/stl_heap.h:335:22: required from ‘void std::__make_heap(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = Date*; _Compare = __gnu_cxx::__ops::_Iter_less_iter]’ /usr/include/c++/6/bits/stl_algo.h:1669:23: required from ‘void std::__heap_select(_RandomAccessIterator, _RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = Date*; _Compare = __gnu_cxx::__ops::_Iter_less_iter]’ /usr/include/c++/6/bits/stl_algo.h:1930:25: required from ‘void std::__partial_sort(_RandomAccessIterator, _RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = Date*; _Compare = __gnu_cxx::__ops::_Iter_less_iter]’ /usr/include/c++/6/bits/stl_algo.h:1945:27: required from ‘void std::__introsort_loop(_RandomAccessIterator, _RandomAccessIterator, _Size, _Compare) [with _RandomAccessIterator = Date*; _Size = int; _Compare = __gnu_cxx::__ops::_Iter_less_iter]’ /usr/include/c++/6/bits/stl_algo.h:1965:25: required from ‘void std::__sort(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = Date*; _Compare = __gnu_cxx::__ops::_Iter_less_iter]’ /usr/include/c++/6/bits/stl_algo.h:4707:18: required from ‘void std::sort(_RAIter, _RAIter) [with _RAIter = Date*]’ user.cpp:60:25: required from here /usr/include/c++/6/bits/predefined_ops.h:56:22: error: no match for ‘operator<’ (operand types are ‘Date’ and ‘Date’) { return *__it < __val; }