Eroare de compilare: user.cpp: In function ‘int main()’: user.cpp:19:11: warning: unused variable ‘j’ [-Wunused-variable] int i,j; ^ 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 ‘void std::__insertion_sort(_RandomAccessIterator, _RandomAccessIterator) [with _RandomAccessIterator = grad*]’: /usr/include/c++/4.8/bits/stl_algo.h:2235:62: required from ‘void std::__final_insertion_sort(_RandomAccessIterator, _RandomAccessIterator) [with _RandomAccessIterator = grad*]’ /usr/include/c++/4.8/bits/stl_algo.h:5476:47: required from ‘void std::sort(_RAIter, _RAIter) [with _RAIter = grad*]’ user.cpp:25:26: required from here /usr/include/c++/4.8/bits/stl_algo.h:2161:13: error: no match for ‘operator<’ (operand types are ‘grad’ and ‘grad’) if (*__i < *__first) ^ /usr/include/c++/4.8/bits/stl_algo.h:2161:13: note: candidates are: 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:2161:13: note: ‘grad’ is not derived from ‘const std::sub_match<_BiIter>’ if (*__i < *__first) ^ 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:2161:13: note: ‘grad’ is not derived from ‘const std::sub_match<_BiIter>’ if (*__i < *__first) ^ 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*) operator<(const sub_match<_Bi_iter>& __lhs, ^ /usr/include/c++/4.8/bits/regex.h:1177:5: 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,