Eroare de compilare: In file included from /usr/include/c++/4.8/algorithm:62:0, from user.cpp:3: /usr/include/c++/4.8/bits/stl_algo.h: In instantiation of ‘_RandomAccessIterator std::__unguarded_partition(_RandomAccessIterator, _RandomAccessIterator, const _Tp&) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<Circle*, std::vector<Circle> >; _Tp = Circle]’: /usr/include/c++/4.8/bits/stl_algo.h:2307:70: required from ‘_RandomAccessIterator std::__unguarded_partition_pivot(_RandomAccessIterator, _RandomAccessIterator) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<Circle*, std::vector<Circle> >]’ /usr/include/c++/4.8/bits/stl_algo.h:2338:54: required from ‘void std::__introsort_loop(_RandomAccessIterator, _RandomAccessIterator, _Size) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<Circle*, std::vector<Circle> >; _Size = int]’ /usr/include/c++/4.8/bits/stl_algo.h:5475:36: required from ‘void std::sort(_RAIter, _RAIter) [with _RAIter = __gnu_cxx::__normal_iterator<Circle*, std::vector<Circle> >]’ user.cpp:74:37: required from here /usr/include/c++/4.8/bits/stl_algo.h:2269:19: error: passing ‘const Circle’ as ‘this’ argument of ‘bool Circle::operator<(const Circle&)’ discards qualifiers [-fpermissive] while (__pivot < *__last) ^