In file included from /usr/include/c++/4.8/algorithm:62:0,
                 from Vector.h:4,
                 from Hash.h:6,
                 from main.cpp:7:
/usr/include/c++/4.8/bits/stl_algo.h: In instantiation of ‘_RandomAccessIterator std::__unguarded_partition(_RandomAccessIterator, _RandomAccessIterator, const _Tp&) [with _RandomAccessIterator = OrTerm*; _Tp = OrTerm]’:
/usr/include/c++/4.8/bits/stl_algo.h:2283:70:   required from ‘_RandomAccessIterator std::__unguarded_partition_pivot(_RandomAccessIterator, _RandomAccessIterator) [with _RandomAccessIterator = OrTerm*]’
/usr/include/c++/4.8/bits/stl_algo.h:2315:54:   required from ‘void std::__introsort_loop(_RandomAccessIterator, _RandomAccessIterator, _Size) [with _RandomAccessIterator = OrTerm*; _Size = long int]’
/usr/include/c++/4.8/bits/stl_algo.h:5461:36:   required from ‘void std::sort(_RAIter, _RAIter) [with _RAIter = OrTerm*]’
main.cpp:152:54:   required from here
/usr/include/c++/4.8/bits/stl_algo.h:2245:19: error: passing ‘const OrTerm’ as ‘this’ argument of ‘bool OrTerm::operator<(const OrTerm&)’ discards qualifiers [-fpermissive]
    while (__pivot < *__last)
                   ^