Borderou de evaluare (job #541455)

Eroare de compilare: In file included from /usr/include/c++/4.6/algorithm:63:0, from /usr/include/c++/4.6/i686-linux-gnu/./bits/stdc++.h:64, from user.cpp:1: /usr/include/c++/4.6/bits/stl_algo.h: In function ‘_RandomAccessIterator std::__unguarded_partition(_RandomAccessIterator, _RandomAccessIterator, const _Tp&) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<Pos*, std::vector<Pos> >, _Tp = Pos]’: /usr/include/c++/4.6/bits/stl_algo.h:2253:70: instantiated from ‘_RandomAccessIterator std::__unguarded_partition_pivot(_RandomAccessIterator, _RandomAccessIterator) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<Pos*, std::vector<Pos> >]’ /usr/include/c++/4.6/bits/stl_algo.h:2284:54: instantiated from ‘void std::__introsort_loop(_RandomAccessIterator, _RandomAccessIterator, _Size) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<Pos*, std::vector<Pos> >, _Size = int]’ /usr/include/c++/4.6/bits/stl_algo.h:5407:4: instantiated from ‘void std::sort(_RAIter, _RAIter) [with _RAIter = __gnu_cxx::__normal_iterator<Pos*, std::vector<Pos> >]’ user.cpp:59:25: instantiated from here /usr/include/c++/4.6/bits/stl_algo.h:2215:4: error: passing ‘const Pos’ as ‘this’ argument of ‘bool Pos::operator<(const Pos&)’ discards qualifiers [-fpermissive]